[clang] [llvm] [ValueTracking] Return true for AddrSpaceCast in canCreateUndefOrPoison (PR #144686)

[Wenju He via llvm-commits]

wenju-he wrote:

> For the purposes of this PR, I think you should only change canCreateUndefOrPoison to return true and just eat the regressions. 

done. Please let me know if we should add FIXME for the regression in clang/test/CodeGenOpenCL/amdgcn-buffer-rsrc-type.cl and llvm/test/Transforms/Attributor/reduced/aapointer_info_map_invalidation.ll

The change in clang/test/CodeGenOpenCL/as_type.cl should not be a regression since spir isn't a concrete target.

https://github.com/llvm/llvm-project/pull/144686