Rework PostFX render technique initialization

[TheMostDiligent]

At the moment there is one InitializePSO function that takes a lot of parameters.
A cleaner way would be to have RenderTechniqueBuilder class:

RenderTechniqueBuilder TechBuilder;
TechBuilder
    .AddShader(pVS) // The type can be used to determine which shader to set
    .AddShader(pPS) // PipelineStateCreaeInfoX uses this approach
    .SetDepthStencilState(DSS);
RenderTech = TechBuilder();

On the other hand, maybe this class is not even needed as PipelineStateCreateInfoX can handle many of these tasks.