[AMDGPU][Global-ISel] reuse extension related patterns in td file

However the imported rules can not be used for now because Global ISel
selectImpl() seems has some bug/limitation to create a illegl COPY
from VGPR to SGPR. So currently workaround this by not auto selecting these
patterns.

Fixes #61468

Reviewed By: arsenm

Differential Revision: https://reviews.llvm.org/D147780