pacman: Completely break z80_cpu and z80_env dependency

This is setting up to allow the cpu to emulate other things
pacman: refactor event code out of pacman
Fix the static analysis failures
pacman: Factor out rom loading into a generalized file

Also add search paths!
pacman: Rename z80_env to pacman_machine
pacman: delete an unused enum
gameboy: Introduce a gameboy skeleton
pacman: Fix signatures of callbacks to remove warnings
pacman: Merge pacman/render.c and pacman/pacman.c

This helps with warnings and makes sense to do