[clang] Prefer clang_setup over use_clang
This patch switches over uses of use_clang to clang_setup to fix a
potential race condition that has been impacting CI.
This is split from the refactoring to ensure I'm not missing anything
major here on the clang-tools-extra side.
This should fix #145703.
Reviewers: AaronBallman, HighCommander4, HerrCai0907, petrhosek, Keenuts
Reviewed By: petrhosek
Pull Request: https://github.com/llvm/llvm-project/pull/147437
