AddressSanitizer: Convert tests to opaque pointers

Needed some manual fixes:
  AMDGPU/asan_instrument_generic_address_space.ll
  dynamic-shadow-darwin.ll
  lifetime.ll
  stack-poisoning-byval-args.ll
  global_metadata_windows.ll
  asan-masked-load-store.ll
  stack-poisoning-and-lifetime.ll
  stack-poisoning-and-lifetime-be.ll

This included some of the worst opaquify breakages I've seen. The
tests were dependent on 0 indexed GEPs, and had check lines directly
checking pointee types.