vendor:directx/d3d12: add shader component mapping constants and macro-procedures

[denovodavid]

When creating a d3d12 shader resource view, a component mapping must be provided as the default is non-zero. This PR adds the default value and other constants/macro-procedures from d3d12.h for shader component mapping. It also changes the SHADER_COMPONENT_MAPPING enum type to u32 to match the SHADER_RESOURCE_VIEW_DESC.Shader4ComponentMapping type.

Relevant docs:

• https://learn.microsoft.com/en-us/windows/win32/api/d3d12/ne-d3d12-d3d12_shader_component_mapping#remarks
• https://learn.microsoft.com/en-us/windows/win32/api/d3d12/ns-d3d12-d3d12_shader_resource_view_desc

// example usage
rd.device->CreateShaderResourceView(
    vertex_buffer,
    &d3d12.SHADER_RESOURCE_VIEW_DESC{
        ViewDimension = .BUFFER,
        Shader4ComponentMapping = d3d12.DEFAULT_SHADER_4_COMPONENT_MAPPING,
        Buffer = {
            NumElements = u32(len(vertices)),
            StructureByteStride = size_of(vertices[0]),
        },
    },
    srv_handle,
)