D3D12: SPIRV translation should depend on PipelineLayout

[Kangz]

In the D3D12 backend we generate the HLSL code in the ShaderModule constructor, before we know the pipeline state. The code numbers the descriptors of each type in increasing order for each set. Then the pipeline layout does the same thing independently.

This would make the following break as the shader module would make t2 use the SRV at index 1 in the descriptor range.

layout(set = 0, location = 0) texture2D t0;
layout(set = 0, location = 2) texture2D t2;

nxt::BindGroupLayout = device.CreateBindGroupLayoutBuilder()
    .SetBindingsType(0, 3, nxt::BindingType::SampledTexture, kAllShaderStages)
    .GetResult();