[llvm] [DebugInfo][InstrRef] Treat ORRWrr as a copy instr (PR #123102)

[Jeremy Morse via llvm-commits]

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

LGTM; this is really interesting in that copy-like instructions mutate between being unrecognisable and then recognisable as copies. I wonder if in the long term this might force too much logic into `isCopyInstrImpl`, but this fix to it is good.

I feel the urge to say "this should be an MIR test", but I suppose this is checking how isel produces a copy and how it mutates over the compilation, and that it doesn't crash. So, the test is probably fine as it is.

https://github.com/llvm/llvm-project/pull/123102