ac/nir: Cleanup pre-rasterization output info to avoid repetition.
Based on !28768 (merged) and !28765 (merged)
The AMD common NIR code base has started to become a mess. This MR intends to do some cleanup:
- Move some helper functions and macros that are not used outside of ac/nir, into a separate header
- Don't include
nir_builder.h
in ac/nir headers - Consolidate pre-rasterization stage output information into a single struct and use the same function for gathering information about them.