refactored and cleaned a bit SMWorld class for best practices:
- moved content of Regions.py and Rules.py in SMWorld
- moved appropiate code to their dedicated World core functions
- moved some Entrances being created in generate_basic to create_regions
more comeback check fixes:
- fixed setting progression door openers items local if doors_colors_rando is used
- enable comeback check only for filling stage as later stages (progression balancing, accessibility and spoiler playthrough) are prone to fail with it
67c3076572