[clang] [Driver] Remove ignored Flag form of -fauto-profile/-fprofile-sample-use (PR #113528)

[Fangrui Song via cfe-commits]

MaskRay wrote:

> It's true that there isn't any compatibility argument for leaving `-fprofile-sample/auto` (it was silently ignored afterall), but I think the consistency argument is important. From a standpoint of a clang user, it's very reasonable to expect that `fprofile-use` and `-fprofile-sample-use` will behave similarly, and inconsistent behavior leads to confusion.

I understand the option similarity argument, but I think it's outweighed by the drawback of having a misleading Flag form with a confusing file extension. With `-fprofile-use=`, people do use `default.prof`, but sample PGO uses very different extension names.

https://github.com/llvm/llvm-project/pull/113528