[llvm] [DebugInfo][RemoveDIs] Handle dbg.declares in SelectionDAGISel (PR #73496)

[Jeremy Morse via llvm-commits]

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

LGTM; Matt raises a good point about the bitcast, but as this is just a refactor + adding two new calls to handle dbg.declares stored in DPValues, I think it's best treated elsewhere. We've already got some tickets hanging around about how the handling of debug-info for arguments in SelectionDAG is a bit of a hack.

https://github.com/llvm/llvm-project/pull/73496