Cooperative Vectors: validate builtin parameters

[damyanp]

The parameters to DXIL operations for cooperative vectors are getting checked in DxilValidation, but we should also be validating the parameters at a higher level so that we can report more targetted diagnostics.

See https://github.com/microsoft/DirectXShaderCompiler/pull/7290/files#r2029984142

[damyanp]

See https://devblogs.microsoft.com/directx/shader-model-6-9-and-the-future-of-cooperative-vector/