anv: generated indirect draws optimization
Only enabled on Gfx11+. Gfx9 would require some slightly different shaders to generate VERTEX_BUFFER_STATE
structures.
/cc @fjdegroo : if you want to play with this on TGL. In its current form this MR should work on DG2 too.
This includes !15631 (closed) (just ignore the first 4 patches from @jekstrand for review).
Tested on Assassin's Creed Odyssey where it gives a nice 10fps improvement on A380.
Edited by Lionel Landwerlin