Fix Gitlab::AuthLogger constant resolution

What does this MR do and why?

When trying Packwerk on GitLab codebase as part of PoC'ing extracting components out of the monolith, I noticed that Packwerk was crashing with this error:

/Users/fabiopitino/.asdf/installs/ruby/2.7.5/lib/ruby/gems/2.7.0/gems/packwerk-2.2.0/lib/packwerk/constant_discovery.rb:64:in `rescue in context_for': Ambiguous constant definition: (ConstantResolver::Error)

"Gitlab::AuthLogger" could refer to any of
  lib/gitlab/auth_logger.rb
  ee/lib/gitlab/auth_logger.rb

This is caused by the Gitlab::AuthLogger constant that is defined in both Core and EE. The problem is that the EE extension should be a module instead of overriding the constant.

This MR fixes the constant resolution.

Screenshots or screen recordings

$ FOSS_ONLY=1 rails c

[1] pry(main)> Gitlab::AuthLogger.file_name_noext
=> "auth"

$ rails c

[1] pry(main)> Gitlab::AuthLogger.file_name_noext
=> "auth_json"

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

MR acceptance checklist

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• I have evaluated the MR acceptance checklist for this MR.