Largely similar to D3D12 implementation but more simple buffer
management and no mips scaling. Includes both FBO and FSI
rendering paths.
Tested on Linux with 2x2 and 3x3 running smoothly.
Simplifies emission of the blocks themselves (including inserting blocks
into the function's block list in the correct order), as well as phi after
the branching.
Also fixes 64bpp storing with blending in the fragment shader interlock
render backend implementation (had a typo that caused the high 32 bits to
overwrite the low ones).
Also fixes addressing of MSAA samples 2 and 3 for 64bpp color render targets in the ROV RB implementation on Direct3D 12.
Additionally, with FSI/ROV, alpha test and alpha to coverage are done only if the render target 0 was dynamically written to (according to the Direct3D 9 rules for writing to color render targets, though not sure if they actually apply to the alpha tests on Direct3D 9, but for safety).
There is also some code cleanup for things spotted during the development of the feature.
Put all descriptors used by translated shaders in up to 4 descriptor sets, which is the minimum required, and the most common on Android, `maxBoundDescriptorSets` device limit value
