[llvm] [UTC][LV] Allow running multiple UTC scripts on a single file (PR #212374)

[Luke Lau via llvm-commits]

https://github.com/lukel97 commented:

My first thought is, `llvm-lit --update-tests` would need to be updated to invoke multiple UTC scripts now, same with update_any_test_checks.py. 

But for the specific motivating use case in the loop vectorizer where we have some tests that we want to see both the VPlan and LLVM IR output. Can we just teach the VPlan regexes in ./update_analyze_test_checks.py to also match on the LLVM IR?

https://github.com/llvm/llvm-project/pull/212374