[clang] [Clang] [Sema] Improve support for `__restrict`-qualified member functions (PR #83855)

[Aaron Ballman via cfe-commits]

AaronBallman wrote:

> > @Sirraide, wait, did we all miss this PR? I am so sorry
> 
> This was a while ago, but I recall talking to @AaronBallman about this one several times, and I think our conclusion at some point was that it wasn’t worth supporting this divergent behaviour or sth like that but I could be wrong (we also had a discussion about in one of the Wednesday meetings iirc).

That matches my recollection. Use of `__restrict` on member functions is an outlier to begin with, there's divergence between compilers already, there's a reasonable chance of silent breaking changes by caring about `__restrict` where we didn't used to, so it seemed like we'd want more motivation before going down this path.

https://github.com/llvm/llvm-project/pull/83855