[clang] [clang-tools-extra] WIP: Extend SourceLocation to 64 bits. (PR #146314)

[Erich Keane via cfe-commits]

https://github.com/erichkeane commented:

I did a light pass of the 1st 1/4 of this or so.  The smuggling back and forth to raw-encoding seems strange?  WHy are we doing that here?

Otherwise just minor questions/requested analysis.

FWIW, I'm reasonably comfortable with just pulling this band-aid, but the Area Team probably needs to make the determination (and we need to spend more time on this review).

https://github.com/llvm/llvm-project/pull/146314