[amdgpu] D2D memcpy via streams and HSA (#69977)

hsa_amd_memory_async_copy can handle device to device copies if passed
the corresponding parameters.

No functional change - currently D2D copy goes through a fallback in
libomptarget that stages through a host malloc, after this it goes
directly through HSA.

Works under exactly the situations that HSA works. Verified locally on a
performance benchmark. Hoping to attract further testing from internal
developers after it lands.