Merge branch 'ps/t7527-fix-tap-output'

Merge branch 'ps/t7527-fix-tap-output'

A recent regression in t7527 that broke TAP output has been fixed,
some other test noise that also broke TAP output has been silenced,
and 'prove' is now configured to fail on invalid TAP output to
prevent future regressions.

* ps/t7527-fix-tap-output:
  t: let prove fail when parsing invalid TAP output
  t/lib-git-p4: silence output when killing p4d and its watchdog
  t/test-lib: silence EBUSY errors on Windows during test cleanup
  t7810: turn MB_REGEX check into a lazy prereq
  t7527: fix broken TAP output
  ci: unify Linux images across GitLab and GitHub
  gitlab-ci: add missing Linux jobs
  gitlab-ci: rearrange Linux jobs to match GitHub's order