Deny manual tests in new PRs

[andy31415]

We should not allow manual CI steps in PRs. Manual tests are anything that requires the user to look at logs, generally identified via a verification tag in yaml files. For an example see #34614 (Test_TC_TSTAT_4_2.yaml has several manual steps in that PR)

Note that existing tests may already be manual so we cannot blanket-check all files. What we want is:

• check against files changed in the PR only
• allow a bypass label for the check (we could use a github label or for failing files check for some "why it is bypassed" comment in a specific format)
• reject any yaml test files that have the text ^\s*verification: in them.

[cecille]

#35493