Consolidate ref checking logic for FE and BE

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Background

The following discussion from !101930 (merged) should be addressed:

• @mrincon started a discussion: (+1 comment)

  Suggestion (non-blocking): We have a very similar regex here: https://gitlab.com/gitlab-org/gitlab/blob/master/lib/api/validations/validators/git_ref.rb#L12

  Maybe we can use the same list or cross link these with comment?

Problem to solve

• We should investigate how to best consolidate the regex / checks we use for refs:
  • https://gitlab.com/gitlab-org/gitlab/blob/master/lib/api/validations/validators/git_ref.rb#L12
  • https://gitlab.com/gitlab-org/gitlab/-/blob/7359d23f4e078479969c872924150219c6f1665f/app/assets/javascripts/new_branch_form.js#L41
  • !101930 (diffs)
• Move related utils to a !101930 (comment 1286465451) (if it still makes sense)