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

[via llvm-commits]

https://github.com/NeKon69 commented:

> Obviously these annotations should exist but it appears they were added based manual review but there's compiler warnings for them which provide suggestions. I think this should be a tool-driven change to make sure the existing functionality works/is complete.

It would be nice to have some initial tool-driven annotation placement, but since most of the llvm codebase is still not annotated with those attributes, we won't get all of the suggestions right. So manual placement based on "review and add" is still required.

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