Fix 8601 check for RayQuery user type

[brendan-duncan]

Fixes #8601

Compiling to SPIR-V crashes when a user-defined struct or class is named
RayQuery (a reserved intrinsic name), e.g. a ray-tracing abstraction that
declares its own RayQuery type inside a namespace.

HLSL has no rule forbidding this; the local declaration should shadow the
reserved name, and the struct should compile like any other.

Added tools/clang/test/CodeGenSPIRV/type.rayquery.user-defined-shadow.hlsl,
which reproduces the issue and checks that the shadowing struct lowers to a
normal OpTypeStruct and that no OpTypeRayQueryKHR is emitted.

Verified that the intrinsic RayQuery still lowers to OpTypeRayQueryKHR
and that existing rayquery CodeGenSPIRV tests continue to pass.

[azure-pipelines]

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[brendan-duncan]

@microsoft-github-policy-service agree

[llvm-beanz]

Thank you for this contribution!

I'm happy with this PR as-is, but I do (oddly) recommend removing the comments. I realize the comments do explain well the code and why it differs from the code around it, but all the code around it is also a mess of bugs that should change because string-matching type names is bad.

[brendan-duncan]

Agreed with the comment removal. I was debating that myself.