[llvm] [ADT] Add `[[clang::lifetimebound]]` annotations to Twine.h (PR #210474)

[via llvm-commits]

https://github.com/isuckatcs requested changes to this pull request.

I'm not sure about some of the annotaions. I guess they should be double checked just in case.

https://github.com/llvm/llvm-project/pull/210474