Run ci validation in MR pipelines

What does this MR do and why?

Add rspec ci-config-validation job to MR pipelines changing CI configuration files.

Things to note:

1. This new job is expected to be slow, because evaluating our pipeline yaml is time consuming due to its current size and complex logic.

   • The job current takes 27 minutes 16 seconds to run, which is significant for the critical path, as the entire tier-1 MR pipeline only takes 31 minutes 54 seconds.
   • I don't think we need to be concerned with this run time, as it will only run in MRs that are updating CI configurations which is a very small portion of MRs.

2. The job can be skipped with pipeline:skip-ci-validation.

   • This has been tested in the following pipeline which does not have the rspec ci-config-validation job after label is added:
   • Ruby 3.2.4 MR [tier:1, types:qa,code,rspec-predictive, opts:skip-ci-validation].

3. Regarding the danger alerts listed in CI Jobs Dependency Validation, I have verified that they are false negatives.

For the future:

• We can also consider parallelization in the future. But since all tests are written in 2 files, we can't parallelize them yet.

Re: #34040 (closed)

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