nvk: add support for D32_SFLOAT_S8_UINT
This adds support for the D32 S8 format needed for things like zink
This allocates a temporary alongside the image for the stencil copies as an R16_UINT. Then the copies are done in two stages, one from the D32S8 Z component into R16_UINT and then from R16_UINT to R8_UINT and vice-versa.