[HLSL][SPIR-V] Add create.handle intrinsic (#81038)

Add a SPIR-V target-specific intrinsic for creating handles, which is
used for lowering HLSL resources types like RWBuffer.

`llvm/lib/TargetParser/Triple.cpp`: SPIR-V intrinsics use "spv" as the
target prefix, not "spirv". As far as I can tell, this is the first one
that is used via the `CGBuiltin` codepath, which relies on
`getArchTypePrefix`, so I've corrected it here.

`clang/lib/Basic/Targets/SPIR.h`: When records are laid out in the
lowering from AST to IR, they were incorrectly offset because these
Pointer attributes were defaulting to 32.

Related to #81036