Add header file to define cooperative matrices in spir-v

[s-perron]

This pr will introduce the HLSL standard header files. This will become the a
way to add new extensions to HLSL without having to make modifications to the
compiler.

This first example is a fairly complex example that demonstrates how to do a few
different things:

1. Trying to create a simple class interface that allows the compiler to
   naturally enforce the validation rules. In this case, we might be more strict
   than the spir-v validation, but I believe this is still usable.
2. How to create a builtin that can be expanded by the spir-v backend. The
   OpCooperativeMatrixLengthKHR instruction does not have an interface that is
   natural in a language like HLSL. However, we can define a function that is, and
   have the backend, make small adjustments. These cases should be avoided as much
   as possible.

[s-perron]

@EpicJeanNoeMorissette FYI: You said you were interested in seeing this when it was ready to be made public. This will probably still go through some changes before it is merged, but this is the vision I have.

[github-actions]

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