Z-prepass for Quick3D with RHI

Also called depth prepass. Do not confuse with "depth pass" which refers to generating a depth texture in a separate renderpass that then serves as input to a certain technique (such as, SSAO), custom material or effect. Z-prepass does not generate a separate texture, it rather renders targeting the same depth-stencil buffer that will then be used with the main rendering "pass". And it is done as part of the main render pass.