Replace Tooling::TestFileFinder with test_file_finder gem

What does this MR do?

Replace Tooling::TestFileFinder with test_file_finder gem when finding foss tests.

https://gitlab.com/gitlab-org/ci-cd/test_file_finder/-/merge_requests/13 adds custom mapping for the test_file_finder gem through a yml file.

Closes #239257 (closed)

Example rspec foss impact job based on test_file_finder https://gitlab.com/gitlab-org/gitlab/-/jobs/699881848.

• change to ee/app/controllers/ee/autocomplete_controller.rb triggered FOSS test app/controllers/autocomplete_controller_spec.rb
• change to ee/app/controllers/projects/audit_events_controller.rb did not trigger any FOSS test as it has no related FOSS code

Screenshots

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team