radeonsi: misc changes prepare for mono ps aco support
These changes are for monolithic PS use ACO.
- ACO expect nir lower all resource from index to descriptor, so need to call
nir_lower_non_uniform_access
for divergent resource. Previously radeonsi did in LLVM for this, now switch to rely on non_uniform tag too. - Other commits just for simplify implementation as ACO does not implement them.