[clang] [clang][SourceManager] Use `getFileLoc` when computing `getPresumedLoc` (PR #166255)

[Aaron Ballman via cfe-commits]

https://github.com/AaronBallman approved this pull request.

LGTM, I think the new diagnostic locations make more sense.

https://github.com/llvm/llvm-project/pull/166255