[OpenMP] Increase opportunity for parallel kernel launch in AMDGPUs: add...

[OpenMP] Increase opportunity for parallel kernel launch in AMDGPUs: add multiple hsa queue's per device in plugin
This patch extends the AMDGPU plugin for OpenMP target offloading from using a single HSA queue to multiple queues (four in this patch) per device. This enables concurrent threads to concurrently submit kernel launches to the same GPU.

Reviewed By: JonChesterfield

Differential Revision: https://reviews.llvm.org/D115771