anv: Refactor image creation
This doesn't rewrite the world. It just rearranges and deduplicates some things.
- Move creation of aux surfaces into its own function.
- Reduce the indentation in the if-tree for aux surfaces from 5 to 3 by flattening some logic.
- Deduplicate the same aspect loop found in Android code and core code.
I sanity-tested on Sky Lake with 'dEQP-VK.texture.filtering.2d.*'. No regressions there.