[clang] [clang-cl] Support /std:clatest (PR #147284)

[Aaron Ballman via cfe-commits]

AaronBallman wrote:

> > You've got the same typo (?) in a bunch of places. You have `/stdc:latest` instead of `/std:clatest`. Same for `/std:c++latest`.
> 
> Good catch! Sheesh, fingers. Work!

Those are all addressed. This is what I get for typing `__STDC_*` as often as I do. :-D

https://github.com/llvm/llvm-project/pull/147284