[HLSL] Enable clang extension matrices in HLSL

[pow2clk]

Matrices need to be available whenever compiling HLSL. They will ultimately need to meet the constraints and capabilities of HLSL matrices, but for this issue to be resolved, we just need to make them available and have their template aliases predefined so that the short versions can be defined in the hlsl_basic_types.h header similarly to how extvectors are set up there.

[llvmbot]

@llvm/issue-subscribers-clang-codegen

Author: Greg Roth (pow2clk)

Matrices need to be available whenever compiling HLSL. They will ultimately need to meet the constraints and capabilities of HLSL matrices, but for this issue to be resolved, we just need to make them available and have their template aliases predefined so that the short versions can be defined in the hlsl_basic_types.h header similarly to how extvectors are set up there.