[llvm] [Offload] Add olLaunchKernelSuggestedGroupSize (PR #142130)

[Joseph Huber via llvm-commits]

https://github.com/jhuber6 commented:

How does this recommend a size without additional information? Just guesses what would give the GPU full occupancy? Seems like something the user should know and if it's something SYCL wants to provide it should be done at that layer.

https://github.com/llvm/llvm-project/pull/142130