[llvm] [AMDGPU][NewInsertWaitcnts] Boilerplate for the new wait insertion pass (PR #226335)

[Pierre van Houtryve via llvm-commits]

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+# NOTE: Assertions have been autogenerated by utils/update_mir_test_checks.py UTC_ARGS: --version 6
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Pierre-vh wrote:

I'd vote for putting this in a separate test sub-folder though. I think doing those are fine.
It'd allow us to keep the names a bit shorter too.

https://github.com/llvm/llvm-project/pull/226335