Support `@llvm.spv.resource.nonuniformindex` in SPIRV Codegen.
- Add `NonUniformEXT` decoration to the registers marked as
`nonuniformindex`, and recursively decorate its child registers (e.g.
Copy, AccessChain, Load) that access such index.
- `OpCapability ShaderNonUniformEXT` is already added in the code.
-
[SPV_EXT_descriptor_indexing](https://github.khronos.org/SPIRV-Registry/extensions/EXT/SPV_EXT_descriptor_indexing.html)
is skipped because it's added to SPIRV Core in 1.5.
## Unit test
- The unit test checks that the register being used in the final
Store/Load/Write instruction is decorated, as required by the spec.
- The implementation follows [DXC](https://godbolt.org/z/zhqGThcaf) in
that it recursively decorates all the child elements until the end.
```hlsl
RWStructuredBuffer<uint4> StructuredOut[64];
RWBuffer<uint> UnStructuredOut[64];
[numthreads(64,1,1)]
void main(uint3 GTID: SV_GroupThreadID) {
StructuredOut[(NonUniformResourceIndex(GTID.x + 1))][98][0] = 99;
UnStructuredOut[(NonUniformResourceIndex(GTID.x))][96] = 95;
}
```
Resolves https://github.com/llvm/llvm-project/issues/160231,
https://github.com/llvm/llvm-project/issues/161852.
Verified
[offload-test-suite](cfc37840c8/test/Feature/ResourceArrays/unbounded-array-nuri.test)
started passing for clang.
56c604961e