Improve compatibility with Semantic Logger (#5238)

Semantic Logger returns Symbol for `#level`:
```
[1] pry(main)> SemanticLogger[Sidekiq].level
=> :debug
```
so current code fails with
```
[2] pry(main)> Sidekiq.logger = SemanticLogger[Sidekiq]
=> #<SemanticLogger::Logger:0x00007f1d27984a18 @filter=nil, @level=nil, @level_index=nil, @name="Sidekiq">
[3] pry(main)> Sidekiq.logger.debug?
ArgumentError: comparison of Symbol with 0 failed
from /home/ojab/.rbenv/versions/3.1.1/lib/ruby/gems/3.1.0/gems/sidekiq-6.4.1/lib/sidekiq/logger.rb:39:in
`<='
```
Calling `#{level}?` methods on the logger directly instead of
comparing `#level` with integer fixes that.

lib/sidekiq.rb

@@ -204,12 +204,12 @@ module Sidekiq
   end
 
   def self.logger
-    @logger ||= Sidekiq::Logger.new($stdout, level: Logger::INFO)
+    @logger ||= Sidekiq::Logger.new($stdout, level: :info)
   end
 
   def self.logger=(logger)
     if logger.nil?
-      self.logger.level = Logger::FATAL
+      self.logger.fatal!
       return self.logger
     end
 

lib/sidekiq/logger.rb

@@ -35,24 +35,10 @@ module Sidekiq
       nil
     end
 
-    def debug?
-      level <= 0
-    end
-
-    def info?
-      level <= 1
-    end
-
-    def warn?
-      level <= 2
-    end
-
-    def error?
-      level <= 3
-    end
-
-    def fatal?
-      level <= 4
+    LEVELS.each do |level, numeric_level|
+      define_method("#{level}?") do
+        local_level.nil? ? super() : local_level <= numeric_level
+      end
     end
 
     def local_level

test/test_job_logger.rb

@@ -93,4 +93,36 @@ class TestJobLogger < Minitest::Test
     log_level_warning = @output.string.lines[0]
     assert_match(/WARN: Invalid log level/, log_level_warning)
   end
+
+  def test_custom_logger_with_non_numeric_levels
+    logger_class = Class.new(Logger) do
+      def level
+        :nonsense
+      end
+
+      def info?
+        true
+      end
+
+      def debug?
+        false
+      end
+    end
+
+    @logger = logger_class.new(@output, level: :info)
+    Sidekiq.logger = @logger
+
+    jl = Sidekiq::JobLogger.new(@logger)
+    job = {"class" => "FooWorker", "log_level" => "debug"}
+
+    assert @logger.info?
+    refute @logger.debug?
+    jl.prepare(job) do
+      jl.call(job, "queue") do
+        assert @logger.debug?
+      end
+    end
+    assert @logger.info?
+    refute @logger.debug?
+  end
 end