[clang] [Feat] Allow Finding across only parts of an AST. (PR #127423)

[Michael Spencer via cfe-commits]

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

I think this is good from the modules end and I get how the predicate can be useful. My only concern is that this feels a bit like another matcher that's not using the matcher API, so I'd like someone more familiar with it to also approve, maybe @5chmidti or @HighCommander4.

https://github.com/llvm/llvm-project/pull/127423