Run-pass checks for warnings, notes, etc. #59659
Description
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.