AMDGPU: Update some tests to use opaque pointers

vectorize-buffer-fat-pointer.ll required a manual check line fix.
vector-alloca-addrspacecast.ll required a manual fixup of a check
line. partial-regcopy-and-spill-missed-at-regalloc.ll required
re-running update_mir_test_checks. The HSA metadata tests required
avoiding the script touching the type name in the metadata.

annotate-noclobber.ll ran into one update script bug. It deleted a
check line with a 0 offset GEP, moving the following -NEXT check
logically up one line.