[llvm] [OpenMP] Add support for custom callback in AMDGPUStream (PR #112785)

[Joseph Huber via llvm-commits]

jhuber6 wrote:

@ronlieb @jplehr @dhruvachak AMD version https://gist.github.com/jhuber6/09718c6834071957a790e95ee37000b9. I was trying to port it to use the proper interface, but the type you crammed into OMPT is non-trivial due to `std::unique_ptr` so I just worked around it being a weird separate thing.

https://github.com/llvm/llvm-project/pull/112785