[llvm] [LLVM][NVPTX] Add NVPTX codegen support for clusterlaunchcontrol instruction (PR #134568)

[Alex MacLean via llvm-commits]

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

LGTM. Please wait for other reviewers before landing.

As a side note, all the NVPTXISelLowering code and custom nodes seem like they could be eliminated if only we fully supported `i128` types as legal. This has been on my list for a while and perhaps this is a sign I need to come back to it. 

https://github.com/llvm/llvm-project/pull/134568