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

[Shilei Tian via llvm-commits]

shiltian wrote:

> Currently this is handled by the thread
that does the waiting for the kernel to finish. However, this is not sound on NVIDIA architectures and only works for async launches in the OpenMP model that uses helper threads.

I thought we just take advantage of the fact that when we finish launching the kernel, the thread (no matter whether it is helper thread or regular thread), it is waiting there anyway?

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