[clang] [Clang] Cache AST context lookup for declarations (NFC) (PR #223047)

[Mehdi Amini via cfe-commits]

joker-eph wrote:

Here is the "official" (Or I should say "independent") run: https://llvm-compile-time-tracker.com/compare.php?from=4aeec5992e4815b436a01967fc66e174f489ea15&to=99a9b8e86fdf154cee802677541c5a562cc3b36f&stat=instructions:u

https://github.com/llvm/llvm-project/pull/223047