[llvm] [Offload] Move RPC server handling to a dedicated thread (PR #112988)

[Shilei Tian via llvm-commits]

https://github.com/shiltian commented:

Creating extra thread can be tricky because there are cases that people don't like extra thread created. For example, QMCPack disables hidden helper thread due to this reason. Some search online shows that `CUDA_LAUNCH_BLOCKING` is actually a debug feature. IMHO we can just claim that this is not supported (TBH we don't have to support things prefix with either `CUDA` or `HIP`), but users can still choose to use at their discretion.

https://github.com/llvm/llvm-project/pull/112988