[AMDGPU][MC] Fix handling of A16 operands in intersect_ray instructions.

The patch adds the support for 'noa16' operands in non-A16 variants of
the instructions, fixes validation of A16 operands and eliminates the
custom conversion to MCInst.

Part of <https://github.com/llvm/llvm-project/issues/62629>.

Reviewed By: arsenm

Differential Revision: https://reviews.llvm.org/D155057