[llvm] [NFC] Split portions of DWARFDataExtractor into new class (PR #140096)

[David Blaikie via llvm-commits]

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

(I guess one other alternative would be to have a "Resolver" member that's a std::function, then there's only one DWARFDataExtractor and a null resolver V a non-null resolver, perhaps - but I don't know that that's objectively better, and the resolver-builder would have to live in a different header so it didn't introduce the compile-time depnedence you're trying to avoid, which feels a bit awkward, etc)

https://github.com/llvm/llvm-project/pull/140096