[llvm] [workflows] Add post-commit job that periodically runs the clang static analyzer (PR #94106)

[Simon Pilgrim via llvm-commits]

RKSimon wrote:

We used to test on coverity as well: https://scan.coverity.com/projects/llvm - but that broke some time ago and has proven tricky to keep running

https://github.com/llvm/llvm-project/pull/94106