[clang] [Driver][BoundsSafety] Add -fexperimental-bounds-safety flag (PR #70480)

[Yeoul Na via cfe-commits]

rapidsna wrote:

> However, implementing the checking in clang/lib/Driver is much more common. clang/lib/Frontend/CompilerInvocation.cpp has some checking, but the majority is in clang/lib/Driver.

@MaskRay To be clear, the check is now in Driver as you suggested. It's just that the frontend also has some extra checks too. So, you want me to remove the extra checks in the frontend?

https://github.com/llvm/llvm-project/pull/70480