[llvm] [DebugInfo][InstrRef] Index DebugVariables and some DILocations (PR #99318)

[Jeremy Morse via llvm-commits]

jmorse wrote:

/me squints -- so after merging with 2 weeks of master I see the test-change has undone itself. Furthermore, my earlier analysis about it changing to RPO order is wrong because that test function (foo) contains straight line code. Not sure what happened there, but it's even more correct now.

https://github.com/llvm/llvm-project/pull/99318