[HLSL] `[WaveSize]` entry attribute

[llvm-beanz]

Shader Model 6.6 introduced the [WaveSize] attribute:

https://microsoft.github.io/DirectX-Specs/d3d/HLSL_SM_6_6_WaveSize.html

This task does not require WaveSize Range

Dependent on generating the PSV0 task: [incoming]

AC:

• Parse the attribute
• Generate metadata
• has validation of the attribute
• collect wave size in DxilMetadataAnalysis

[davidcook-msft]

@pow2clk to create the work item for the PSV0 generation