[clang] [clang][sema] Add nonnull attribute to builtin format functions (PR #160988)

[Erich Keane via cfe-commits]

https://github.com/erichkeane commented:

This is very much in @AaronBallman 's range here, particularly with the C stuff.  I don't see anything of question, so it is just a matter of whether he thinks this is a good idea.  he's supposed to come back any day now (maybe next week?) so please ping him in another week+ if you don't hear from him.

https://github.com/llvm/llvm-project/pull/160988