[llvm] [KeyInstr] Add fields to DILocation behind compile time flag (PR #133477)

[Jeremy Morse via llvm-commits]

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

LGTM. Bitcode changes to come later or something?

For the record, we're aware this change causes memory consumption to tick up, hence it's behind a flag for now and we've got a few improvements like #134677 to make it tick down.

https://github.com/llvm/llvm-project/pull/133477