* Core: create the per world random object in the world constructor
* remove the check that multiworld exists
* add a deprecation warning to per_slot_randoms
* move random import and fix conflicts
* assert worlds don't exist before setting the multiworld seed
* fix the dlcq and sdv tests
* actually use the seed
"Added a bunch of tests to make sure I don't break anything during refactoring
Huge cleanup in the Regions file, extract methods, remove code duplicate, fix typos, fix variable naming conventions, etc.
Small cleanup in other places, minor stuff just what was needed for Regions"
