Suggest to run RUN AS-IF-FOSS when too many test files detected in rspec foss-impact

What does this MR do?

To avoid rspec foss-impact timing out when there are many FOSS test files to be run, the job will fail with an advise to run all *-as-if-foss jobs for the merge request.

Example pipelines:

• without RUN AS-IF-FOSS https://gitlab.com/gitlab-org/gitlab/-/pipelines/156623044
  • rspec foss-impact is created and failed with instruction message: https://gitlab.com/gitlab-org/gitlab/-/jobs/596759453
• with RUN AS-IF-FOSS https://gitlab.com/gitlab-org/gitlab/-/pipelines/156624483
  • as-if-foss jobs are created
  • rspec foss-impact is not created

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

Closes #220883 (closed)