Enable `Style/MapToHash` cop

Ruby 2.6 added block argument processing to `Enumerable#to_h`.
https://bugs.ruby-lang.org/issues/15143

Rails 7 requires Ruby 2.7.0 or higher, so the new feature can use it.
`Style/MapToHash` cop will detect it. And this cop in the `Style` department,
but this seems to improve performance as follows:

```ruby
# map_to_hash.rb
require 'benchmark/ips'

ARRAY = (1..100).to_a
HASH = {foo: 1, bar: 2}

Benchmark.ips do |x|
  x.report('array.map.to_h') { ARRAY.map { |v| [v, v * 2] }.to_h }
  x.report('array.to_h')     { ARRAY.to_h { |v| [v, v * 2] } }

  x.compare!
end

Benchmark.ips do |x|
  x.report('hash.map.to_h') { HASH.map { |k, v| [k.to_s, v * 2] }.to_h }
  x.report('hash.to_h')     { HASH.to_h { |k, v| [k.to_s, v * 2] } }

  x.compare!
end
```

```console
% ruby map_to_hash.rb
Warming up --------------------------------------
      array.map.to_h     9.063k i/100ms
          array.to_h     9.609k i/100ms
Calculating -------------------------------------
      array.map.to_h     89.063k (± 3.9%) i/s -    453.150k in  5.096572s
          array.to_h     96.449k (± 1.7%) i/s -    490.059k in  5.082529s

Comparison:
          array.to_h:    96448.7 i/s
      array.map.to_h:    89063.4 i/s - 1.08x  (± 0.00) slower

Warming up --------------------------------------
       hash.map.to_h   106.284k i/100ms
           hash.to_h   149.354k i/100ms
Calculating -------------------------------------
       hash.map.to_h      1.102M (± 2.2%) i/s -      5.527M in   5.019657s
           hash.to_h      1.490M (± 0.9%) i/s -      7.468M in   5.013264s

Comparison:
           hash.to_h:  1489707.0 i/s
       hash.map.to_h:  1101561.5 i/s - 1.35x  (± 0.00) slower
```

`Style/MapToHash` cop ... https://docs.rubocop.org/rubocop/1.25/cops_style.html#stylemaptohash

.rubocop.yml

@@ -159,6 +159,9 @@ Style/FrozenStringLiteralComment:
     - 'actionmailbox/db/migrate/**/*.rb'
     - 'actiontext/db/migrate/**/*.rb'
 
+Style/MapToHash:
+  Enabled: true
+
 Style/RedundantFreeze:
   Enabled: true
 

actiontext/lib/action_text/attachment.rb

@@ -91,7 +91,7 @@ module ActionText
 
     private
       def node_attributes
-        @node_attributes ||= ATTRIBUTES.map { |name| [ name.underscore, node[name] ] }.to_h.compact
+        @node_attributes ||= ATTRIBUTES.to_h { |name| [ name.underscore, node[name] ] }.compact
       end
 
       def attachable_attributes

actiontext/lib/action_text/trix_attachment.rb

@@ -39,10 +39,10 @@ module ActionText
         end
 
         def typecast_attribute_values(attributes)
-          attributes.map do |key, value|
+          attributes.to_h do |key, value|
             typecast = ATTRIBUTE_TYPES[key] || ATTRIBUTE_TYPES[:default]
             [key, typecast.call(value)]
-          end.to_h
+          end
         end
     end
 

actionview/lib/action_view/ripper_ast_parser.rb

@@ -86,11 +86,11 @@ module ActionView
         end
 
         def hash_from_body(body)
-          body.map do |hash_node|
+          body.to_h do |hash_node|
             return nil if hash_node.type != :assoc_new
 
             [hash_node[0], hash_node[1]]
-          end.to_h
+          end
         end
 
         def symbol?
@@ -189,9 +189,9 @@ module ActionView
         parser = RenderCallExtractor.new(code)
         parser.parse
 
-        parser.render_calls.group_by(&:first).collect do |method, nodes|
+        parser.render_calls.group_by(&:first).to_h do |method, nodes|
           [ method.to_sym, nodes.collect { |v| v[1] } ]
-        end.to_h
+        end
       end
     end
   end

activerecord/lib/active_record/connection_adapters/mysql/schema_statements.rb

@@ -57,9 +57,9 @@ module ActiveRecord
               orders = options.delete(:orders)
               lengths = options.delete(:lengths)
 
-              columns = index[-1].map { |name|
+              columns = index[-1].to_h { |name|
                 [ name.to_sym, expressions[name] || +quote_column_name(name) ]
-              }.to_h
+              }
 
               index[-1] = add_options_for_index_columns(
                 columns, order: orders, length: lengths

activerecord/lib/active_record/encryption/encryptable_record.rb

@@ -188,12 +188,12 @@ module ActiveRecord
         end
 
         def build_decrypt_attribute_assignments
-          Array(self.class.encrypted_attributes).collect do |attribute_name|
+          Array(self.class.encrypted_attributes).to_h do |attribute_name|
             type = type_for_attribute(attribute_name)
             encrypted_value = ciphertext_for(attribute_name)
             new_value = type.deserialize(encrypted_value)
             [attribute_name, new_value]
-          end.to_h
+          end
         end
 
         def cant_modify_encrypted_attributes_when_frozen

activestorage/test/service/mirror_service_test.rb

@@ -3,11 +3,11 @@
 require "service/shared_service_tests"
 
 class ActiveStorage::Service::MirrorServiceTest < ActiveSupport::TestCase
-  mirror_config = (1..3).map do |i|
+  mirror_config = (1..3).to_h do |i|
     [ "mirror_#{i}",
       service: "Disk",
       root: Dir.mktmpdir("active_storage_tests_mirror_#{i}") ]
-  end.to_h
+  end
 
   config = mirror_config.merge \
     mirror:  { service: "Mirror", primary: "primary", mirrors: mirror_config.keys },