[llvm] Reland "[DebugInfo][DwarfDebug] Separate creation and population of abstract subprogram DIEs" (PR #160786)

[Jeremy Morse via llvm-commits]

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

LGTM; I feel this masks the overall issue identified in the linked issue (i.e. DIE creation is relying on an assumption that's very easy to be false), but we can save that for another day.

https://github.com/llvm/llvm-project/pull/160786