[clang] [llvm] spirv: implement lowering for HLSL Texture2D sampling intrinsics (PR #179322)

[Steven Perron via cfe-commits]

s-perron wrote:

This PR is stacked on https://github.com/llvm/llvm-project/pull/179312. Just review the last PR.

https://github.com/llvm/llvm-project/pull/179322