[Clang] Port ulimit tests to work with internal shell
Now that ulimit is implemented for the internal shell, we can make sure
that the clang tests utilizing ulimit actually work. One just needs the
removal of its shell requirement while the other one needs some rework
to avoid bash for loops. These are writtein in Python for about the same
amount of complexity.
Reviewers: ilovepi, cmtice, AaronBallman, Sirraide, petrhosek
Reviewed By: ilovepi
Pull Request: https://github.com/llvm/llvm-project/pull/157977
