Remove dependency on logger

[eregon]

• To fix the Ruby 3.3.5 warnings: https://github.com/ruby-concurrency/concurrent-ruby/issues/1061
• concurrent-ruby only uses 7 constants from Logger, so just copy those over.

This should be fully compatible and address the warnings. Only if one uses the long-deprecated Concurrent.create_stdlib_logger they might need to add logger to their Gemfile.

[kbrock]

@ioquatix What did you just ask?

1. Can we drop the method that creates @logger It was introduced to prevent a deadlock and do we still need it? 1
2. Can drop global logger and have log be a no-op if @logging does not exist? 2
3. Can we drop all references to the log method? [3]
4. Other.

[ioquatix]

Probably (1) and (3) - basically remove it entirely.