dzn: Basic subgroups

This adds the minimal amount of (real) subgroup support needed for VK1.1. I could've gone with the subgroup size of 1 and then just nop'd all of these, but DXIL supports them so 🤷. We also have ballots and quads but I haven't looked closely enough to see what maps nicely.

Related: #7905 (closed)
/cc @RandomShaper