[AMDGPU] Add GFX12 S_WAIT_* instructions (#77336)

GFX12 has separate wait instructions per counter e.g. S_WAIT_LOADCNT.
S_WAITCNT still exists but is deprecated and codegen should stop using
it. S_WAITCNT_* (e.g. S_WAITCNT_VSCNT) are removed.

This patch adds/removes MC layer support for these instructions.