Move the aux transition state machine code to ISL
This MR a prototype for Moves a bunch of the duplicated aux code in i965 and iris to ISL. It's very similar to !2957 (merged) with a few differences:
- Instead of copying the interface used by i965, it makes things look a bit more like Vulkan. In order to unify things into a single "transition" function, I added a new
ISL_AUX_OP_DRAW
which I think worked out well. - I made no attempt to make aux "nicer" by adding a metadata table. Instead I just added a couple of useful helper functions. This is likely not a good thing; I think some sort of "how does this type of aux work?" metadata table is a good idea; I was more focussed on the external ISL interface so I did the minimal thing.