[rubygems/rubygems] Completely drop base parameter from index

This parameter was coupling the concept of lockfile with the index. I
don't think it's necessary.

Also I believe it's causing some flaky test failures, which might leak
into realworld issues. They are like this:

````
Invoking `/opt/hostedtoolcache/Ruby/3.0.4/x64/bin/ruby -I/home/runner/work/rubygems/rubygems/bundler/spec -r/home/runner/work/rubygems/rubygems/bundler/spec/support/artifice/fail.rb -r/home/runner/work/rubygems/rubygems/bundler/spec/support/hax.rb /home/runner/work/rubygems/rubygems/bundler/tmp/1/gems/system/bin/bundle lock` failed with output:
----------------------------------------------------------------------
--- ERROR REPORT TEMPLATE -------------------------------------------------------

```
NoMethodError: undefined method `identifier' for #<Gem::Specification:0x00005639ad0db0a0 @extension_dir=nil, @full_gem_path=nil, @gem_dir=nil, @ignored=nil, @bin_dir=nil, @cache_dir=nil, @cache_file=nil, @doc_dir=nil, @ri_dir=nil, @spec_dir=nil, @spec_file=nil, @gems_dir=nil, @base_dir=nil, @loaded=false, @activated=false, @loaded_from=nil, @original_platform="ruby", @installed_by_version=nil, @autorequire=nil, @date=2022-07-25 00:00:00 UTC, @description="This is a completely fake gem, for testing purposes.", @email="foo@bar.baz", @homepage="http://example.com", @name="win32-process", @post_install_message=nil, @signing_key=nil, @summary="This is just a fake gem for testing", @version=#<Gem::Version "0.8.3">, @authors=["no one"], @bindir="bin", @cert_chain=[], @dependencies=[<Gem::Dependency type=:runtime name="ffi" requirements=">= 1.0.0">], @executables=[], @extensions=[], @extra_rdoc_files=[], @files=[], @licenses=[], @metadata={}, @platform="ruby", @rdoc_options=[], @require_paths=["lib"], @required_ruby_version=#<Gem::Requirement:0x00005639ad0dbc80 @requirements=[[">=", #<Gem::Version "0">]]>, @required_rubygems_version=#<Gem::Requirement:0x00005639ad0dba50 @requirements=[[">=", #<Gem::Version "0">]]>, @requirements=[], @rubygems_version="3.2.33", @specification_version=4, @test_files=[], @new_platform="ruby", @full_name="win32-process-0.8.3", @has_rdoc=true, @license=["MIT"] win32-process-0.8.3>
  /home/runner/work/rubygems/rubygems/bundler/tmp/rubygems/lib/rubygems/specification.rb:2116:in `method_missing'
  /home/runner/work/rubygems/rubygems/bundler/tmp/1/gems/system/gems/bundler-2.4.0.dev/lib/bundler/remote_specification.rb:115:in `method_missing'
  /home/runner/work/rubygems/rubygems/bundler/tmp/1/gems/system/gems/bundler-2.4.0.dev/lib/bundler/lazy_specification.rb:34:in `eql?'
  /home/runner/work/rubygems/rubygems/bundler/tmp/1/gems/system/gems/bundler-2.4.0.dev/lib/bundler/index.rb:189:in `eql?'
  /home/runner/work/rubygems/rubygems/bundler/tmp/1/gems/system/gems/bundler-2.4.0.dev/lib/bundler/index.rb:189:in `search_by_dependency'
  /home/runner/work/rubygems/rubygems/bundler/tmp/1/gems/system/gems/bundler-2.4.0.dev/lib/bundler/index.rb:96:in `local_search'
  /home/runner/work/rubygems/rubygems/bundler/tmp/1/gems/system/gems/bundler-2.4.0.dev/lib/bundler/index.rb:64:in `unsorted_search'
  /home/runner/work/rubygems/rubygems/bundler/tmp/1/gems/system/gems/bundler-2.4.0.dev/lib/bundler/index.rb:60:in `search'
  /home/runner/work/rubygems/rubygems/bundler/tmp/1/gems/system/gems/bundler-2.4.0.dev/lib/bundler/resolver.rb:179:in `results_for'
  /home/runner/work/rubygems/rubygems/bundler/tmp/1/gems/system/gems/bundler-2.4.0.dev/lib/bundler/resolver.rb:113:in `search_for'
  /home/runner/work/rubygems/rubygems/bundler/tmp/1/gems/system/gems/bundler-2.4.0.dev/lib/bundler/resolver.rb:216:in `block in sort_dependencies'
  /home/runner/work/rubygems/rubygems/bundler/tmp/1/gems/system/gems/bundler-2.4.0.dev/lib/bundler/resolver.rb:207:in `each'
  /home/runner/work/rubygems/rubygems/bundler/tmp/1/gems/system/gems/bundler-2.4.0.dev/lib/bundler/resolver.rb:207:in `sort_by'
  /home/runner/work/rubygems/rubygems/bundler/tmp/1/gems/system/gems/bundler-2.4.0.dev/lib/bundler/resolver.rb:207:in `sort_dependencies'
  /home/runner/work/rubygems/rubygems/bundler/tmp/1/gems/system/gems/bundler-2.4.0.dev/lib/bundler/vendor/molinillo/lib/molinillo/delegates/specification_provider.rb:60:in `block in sort_dependencies'
  /home/runner/work/rubygems/rubygems/bundler/tmp/1/gems/system/gems/bundler-2.4.0.dev/lib/bundler/vendor/molinillo/lib/molinillo/delegates/specification_provider.rb:77:in `with_no_such_dependency_error_handling'
  /home/runner/work/rubygems/rubygems/bundler/tmp/1/gems/system/gems/bundler-2.4.0.dev/lib/bundler/vendor/molinillo/lib/molinillo/delegates/specification_provider.rb:59:in `sort_dependencies'
  /home/runner/work/rubygems/rubygems/bundler/tmp/1/gems/system/gems/bundler-2.4.0.dev/lib/bundler/vendor/molinillo/lib/molinillo/resolution.rb:754:in `push_state_for_requirements'
  /home/runner/work/rubygems/rubygems/bundler/tmp/1/gems/system/gems/bundler-2.4.0.dev/lib/bundler/vendor/molinillo/lib/molinillo/resolution.rb:744:in `require_nested_dependencies_for'
  /home/runner/work/rubygems/rubygems/bundler/tmp/1/gems/system/gems/bundler-2.4.0.dev/lib/bundler/vendor/molinillo/lib/molinillo/resolution.rb:727:in `activate_new_spec'
  /home/runner/work/rubygems/rubygems/bundler/tmp/1/gems/system/gems/bundler-2.4.0.dev/lib/bundler/vendor/molinillo/lib/molinillo/resolution.rb:684:in `attempt_to_activate'
  /home/runner/work/rubygems/rubygems/bundler/tmp/1/gems/system/gems/bundler-2.4.0.dev/lib/bundler/vendor/molinillo/lib/molinillo/resolution.rb:254:in `process_topmost_state'
  /home/runner/work/rubygems/rubygems/bundler/tmp/1/gems/system/gems/bundler-2.4.0.dev/lib/bundler/vendor/molinillo/lib/molinillo/resolution.rb:182:in `resolve'
  /home/runner/work/rubygems/rubygems/bundler/tmp/1/gems/system/gems/bundler-2.4.0.dev/lib/bundler/vendor/molinillo/lib/molinillo/resolver.rb:43:in `resolve'
  /home/runner/work/rubygems/rubygems/bundler/tmp/1/gems/system/gems/bundler-2.4.0.dev/lib/bundler/resolver.rb:50:in `start'
  /home/runner/work/rubygems/rubygems/bundler/tmp/1/gems/system/gems/bundler-2.4.0.dev/lib/bundler/resolver.rb:24:in `resolve'
  /home/runner/work/rubygems/rubygems/bundler/tmp/1/gems/system/gems/bundler-2.4.0.dev/lib/bundler/definition.rb:480:in `reresolve'
  /home/runner/work/rubygems/rubygems/bundler/tmp/1/gems/system/gems/bundler-2.4.0.dev/lib/bundler/definition.rb:283:in `resolve'
  /home/runner/work/rubygems/rubygems/bundler/tmp/1/gems/system/gems/bundler-2.4.0.dev/lib/bundler/definition.rb:181:in `resolve_remotely!'
  /home/runner/work/rubygems/rubygems/bundler/tmp/1/gems/system/gems/bundler-2.4.0.dev/lib/bundler/cli/lock.rb:53:in `run'
  /home/runner/work/rubygems/rubygems/bundler/tmp/1/gems/system/gems/bundler-2.4.0.dev/lib/bundler/cli.rb:674:in `lock'
  /home/runner/work/rubygems/rubygems/bundler/tmp/1/gems/system/gems/bundler-2.4.0.dev/lib/bundler/vendor/thor/lib/thor/command.rb:27:in `run'
  /home/runner/work/rubygems/rubygems/bundler/tmp/1/gems/system/gems/bundler-2.4.0.dev/lib/bundler/vendor/thor/lib/thor/invocation.rb:127:in `invoke_command'
  /home/runner/work/rubygems/rubygems/bundler/tmp/1/gems/system/gems/bundler-2.4.0.dev/lib/bundler/vendor/thor/lib/thor.rb:392:in `dispatch'
  /home/runner/work/rubygems/rubygems/bundler/tmp/1/gems/system/gems/bundler-2.4.0.dev/lib/bundler/cli.rb:31:in `dispatch'
  /home/runner/work/rubygems/rubygems/bundler/tmp/1/gems/system/gems/bundler-2.4.0.dev/lib/bundler/vendor/thor/lib/thor/base.rb:485:in `start'
  /home/runner/work/rubygems/rubygems/bundler/tmp/1/gems/system/gems/bundler-2.4.0.dev/lib/bundler/cli.rb:25:in `start'
  /home/runner/work/rubygems/rubygems/bundler/tmp/1/gems/system/gems/bundler-2.4.0.dev/exe/bundle:48:in `block in <top (required)>'
  /home/runner/work/rubygems/rubygems/bundler/tmp/1/gems/system/gems/bundler-2.4.0.dev/lib/bundler/friendly_errors.rb:120:in `with_friendly_errors'
  /home/runner/work/rubygems/rubygems/bundler/tmp/1/gems/system/gems/bundler-2.4.0.dev/exe/bundle:36:in `<top (required)>'
  /home/runner/work/rubygems/rubygems/bundler/tmp/1/gems/system/bin/bundle:23:in `load'
  /home/runner/work/rubygems/rubygems/bundler/tmp/1/gems/system/bin/bundle:23:in `<main>'
```
````

I think the issue is that now we eagerly materialize some base
specifications before resolving in order to give better errors if user
specified an incorrect source in the Gemfile.

This means that the key for the index hash will have heterogeneous
specification objects (some LazySpecification, some real Specification),
and `LazySpecification#eql?` is incompatible with that.

By dropping the base parameter from the index, we should no longer have
these heterogenous objects as hash keys.

https://github.com/rubygems/rubygems/commit/dc179d41c3

lib/bundler/index.rb

@@ -56,17 +56,17 @@ module Bundler
 
     # Search this index's specs, and any source indexes that this index knows
     # about, returning all of the results.
-    def search(query, base = nil)
-      sort_specs(unsorted_search(query, base))
+    def search(query)
+      sort_specs(unsorted_search(query))
     end
 
-    def unsorted_search(query, base)
-      results = local_search(query, base)
+    def unsorted_search(query)
+      results = local_search(query)
 
       seen = results.map(&:full_name).uniq unless @sources.empty?
 
       @sources.each do |source|
-        source.unsorted_search(query, base).each do |spec|
+        source.unsorted_search(query).each do |spec|
           next if seen.include?(spec.full_name)
 
           seen << spec.full_name
@@ -89,12 +89,12 @@ module Bundler
       self.class.sort_specs(specs)
     end
 
-    def local_search(query, base = nil)
+    def local_search(query)
       case query
       when Gem::Specification, RemoteSpecification, LazySpecification, EndpointSpecification then search_by_spec(query)
       when String then specs_by_name(query)
-      when Gem::Dependency then search_by_dependency(query, base)
-      when DepProxy then search_by_dependency(query.dep, base)
+      when Gem::Dependency then search_by_dependency(query)
+      when DepProxy then search_by_dependency(query.dep)
       else
         raise "You can't search for a #{query.inspect}."
       end
@@ -185,11 +185,9 @@ module Bundler
       @specs[name].values
     end
 
-    def search_by_dependency(dependency, base = nil)
-      @cache[base || false] ||= {}
-      @cache[base || false][dependency] ||= begin
+    def search_by_dependency(dependency)
+      @cache[dependency] ||= begin
         specs = specs_by_name(dependency.name)
-        specs += base if base
         found = specs.select do |spec|
           next true if spec.source.is_a?(Source::Gemspec)
           dependency.matches_spec?(spec)

lib/bundler/resolver.rb

@@ -110,7 +110,7 @@ module Bundler
       dependency = dependency_proxy.dep
       name = dependency.name
       @search_for[dependency_proxy] ||= begin
-        results = results_for(dependency, @base[name])
+        results = results_for(dependency) + @base[name].select {|spec| requirement_satisfied_by?(dependency, nil, spec) }
 
         if vertex = @base_dg.vertex_named(name)
           locked_requirement = vertex.payload.requirement
@@ -175,8 +175,8 @@ module Bundler
       @source_requirements[name] || @source_requirements[:default]
     end
 
-    def results_for(dependency, base)
-      index_for(dependency).search(dependency, base)
+    def results_for(dependency)
+      index_for(dependency).search(dependency)
     end
 
     def name_for(dependency)