[clang] [Bounds Safety][NFC] Add `SemaBoundsSafety` class and move existing Sema checks there (PR #98954)

[Dan Liew via cfe-commits]

delcypher wrote:

> > As noted above `-fbounds-safety` **is a C language extension** which makes it seem like it would fit nicely into the existing division of Sema into multiple objects and relevant source files.
> 
> No, it doesn't fit nicely into the division, which is the reason we're having this discussion.

If we don't agree on this then I must not fully understand what the criteria is for dividing Sema current is.
 
> You can have `SemaBoundsSafety.cpp` and your own "section" inside `Sema.h`, like C++ features do (like templates or lambdas). There's no reason to make separation physical by introducing `SemaBoundsSafety` class from the get-go.

I'm ok with this. Having the implementation in a separate file is where the main benefit lies. The separation into a separation into a separate class is a nice-to-have and ok to drop doing that.

> That's why I propose to follow long-established practice of doing `SemaBoundsSafety.cpp`, and move that around later. What I'd like to evaluate before deciding on `SemaBoundsChecking` is how big its interface is (what would be exposed via `SemaBoundsChecking` class,)

Sure. Let's go with that approach then.



https://github.com/llvm/llvm-project/pull/98954