Run foss impact tests for modified files in `as-if-foss` mode

What does this MR do?

Adds a new job to catch ee dependency in foss by running rspec tests

• Create a class to match a ruby file to its specs
• Create a new job that runs on MR to run foss tests corresponding to changed files

Verification plan

Broken tests in FOSS

Broken FOSS issue	Test MR	Caught by test job in MR? ✅	job duration
#219030 (closed)	!33369 (closed)	https://gitlab.com/gitlab-org/gitlab/-/jobs/572834605 ✅	7 minutes 21 seconds
#219073 (closed)	!33261 (closed)	https://gitlab.com/gitlab-org/gitlab/-/jobs/572714682 ✅	8 mins
#219169 (closed)	!33370 (closed)	https://gitlab.com/gitlab-org/gitlab/-/jobs/572716162 ✅	7 minutes 7 seconds
#219231 (closed)	!33372 (closed)	https://gitlab.com/gitlab-org/gitlab/-/jobs/572835301 ✅	8 minutes 3 seconds
#219313 (closed)	-- unable to revert --
#219401 (closed)	!33373 (closed)	https://gitlab.com/gitlab-org/gitlab/-/jobs/572836299 ✅	6 minutes 8 seconds
#219396 (closed)	!33374 (closed)	https://gitlab.com/gitlab-org/gitlab/-/jobs/572838730 ✅	7 minutes 20 seconds

Fork MR pipeline

!33472 (closed) Job is included in fork MR pipeline: https://gitlab.com/caalberts/gitlab-ee/-/jobs/576628093 ✅

Security MR pipeline

https://gitlab.com/gitlab-org/security/gitlab/-/merge_requests/580 Job is included in security fork MR pipeline: https://gitlab.com/gitlab-org/security/gitlab/-/jobs/576644996 ✅

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

Closes #219262 (closed)