* 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
* Fill: add test for swap error with item rules
https://discord.com/channels/731205301247803413/731214280439103580/1167195750082560121
* Fill: fix swap error found in CI
Swap now assumes the unplaced items can be placed before the to-be-swapped item.
Unsure if that is safe or unsafe.
* Test: clarify docstring and comments in fill swap test
* Test: clarify comments in fill swap test more
Aaron Wagener
PoryGone
black-sliver