Run-pass checks for warnings, notes, etc.

[Centril]

When writing #59658, I found it neccesary to check for warnings in a run-pass test because deny(warning) would observably change the warning pattern I was testing for in the first place.

It would be nice if run-pass would check for WARN, NOTE, HELP, etc. and cause a test failure if those are not found when expected. A bonus point for failing for unexpected WARNs etc. as well.

[petrochenkov]

Looks similar to #56277.

[lcnr]

Is this still relevant? Afaict run-pass tests have been moved to ui

[petrochenkov]

Is this still relevant?

Probably not, but someone needs to check that there's no gratuitous differences between // run-pass UI tests and other UI tests with regards to WARN, NOTE and HELP annotation.