[clang] [clang][modules] Remove preloaded SLocEntries from PCM files (PR #66962)

[Tom Honermann via cfe-commits]

tahonermann wrote:

> That said, isBeforeInTranslationUnit is slow already, and I don't think it's hot in clang, moreso in tools like clang-tidy whose performance is less-critical. So let's make it right, and then optimize it again if problems arise.

It may not be a hot function in Clang itself, but it is quite hot for some downstream Clang forks. While at Coverity, I had to avoid direct use of it because it was far too slow. Anything that speeds it up would be appreciated.

https://github.com/llvm/llvm-project/pull/66962