Improve the regular expression verifications for push rules
Reported here: https://gitlab.com/gitlab-org/gitlab/-/issues/463542#note_1930450440
### Problem
While setting up push rules regular expressions (for example `Require expression in commit messages`), it's not clear if they will work as intended.
Users have to manually test them by pushing commits to the repository until they get an expected result. This is a tedious process.
### Proposal
It would be nice to have a UI tool to verify which commits messages match the regular expression.
issue