[llvm] [AMDGPU] Avoid put implicit_def into bundle that break reg's liveness (PR #142563)

[Jay Foad via llvm-commits]

jayfoad wrote:

Before going much further with this I think it would be good to have a way of directly testing the result of finalizeBundle on an arbitrary sequence of MachineInstrs. If there's no way to do that as a CodeGen test then maybe we need something in unittests?

https://github.com/llvm/llvm-project/pull/142563