[clang] [llvm] Reland "[Utils] Add new --update-tests flag to llvm-lit" (PR #153821)

[Min-Yih Hsu via llvm-commits]

mshockwave wrote:

Please refrain from force push unless necessary: https://llvm.org/docs/GitHub.html#rebasing-pull-requests-and-force-pushes

https://github.com/llvm/llvm-project/pull/153821