ci: Run less jobs upon CI changes

What does this MR do and why?

This changes the strategy to not run everything when any CI config files are changed. We're very reactive when CI config is broken and fixes is usually to revert the change right away, so there's no need to run everything for any CI config change.

Though, maybe we should incentivize to add pipeline:run-all-rspec before merging MRs that touch any CI config file?

Note: There are still jobs that will run when a dependent CI config file is changed, but otherwise, this would reduce the cases where we run a lot of jobs just because a .gitlab/ci/**/* file was changed.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

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

Related to #412895.