WIP: radv: Add support for sparse residency

This is supposed to address (at least in part) #2037 (closed)

cc @bnieuwenhuizen

I initially wanted to start with the host side of things, but I've hit a wall in the shader compiler immediately.

I've only made the first steps to parse OpImageSparseFetch, extract the proper return type and set the TFE flag for that MIMG instruction in ACO. I need to figure out how to let the compiler know that DST+1 is going to hold a bitmask with threads that didn't have resident data, and pipe that into the OpSparseTexelsResident.