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

[David Blaikie via llvm-commits]

dwblaikie wrote:

A more detailed description of the restructuring might be helpful for high level review (though hopefully most of that could be covered on an/the RFC thread, rather than in code review) - specifically the description doesn't mention the addition of virtual dispatch, which seems like a pretty significant change to the way things work.

Alternatively this could use some kind of CRTP instead?

(& virtual dispatch, plus potentially polymorphic ownership (virtual dtor - by default I'd expect non-polymorphic ownership, using a protected non-virtual dtor, and final derived classes, unless there's an expectation/need for polymorphic ownership, which I'd be a bit surprised by))

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