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

This job will run once per day on the main branch, and for every commit
on a release branch. It currently only builds llvm, but could add more
sub-projects in the future.

OpenSSF Best Practices recommends running a static analyzer on software
before it is released:
https://www.bestpractices.dev/en/criteria/0#0.static_analysis