Core: Attribute per slot random directly to the World and discourage using MultiWorld's random (#1649)

* add a random object to the World

* use it in The Messenger

* the worlds don't exist until the end of set options

* set seed in lttp tests

* use world.random for shop shuffle

worlds/alttp/test/inverted/TestInverted.py

@@ -15,6 +15,7 @@ from worlds import AutoWorld
 class TestInverted(TestBase):
     def setUp(self):
         self.multiworld = MultiWorld(1)
+        self.multiworld.set_seed(None)
         args = Namespace()
         for name, option in AutoWorld.AutoWorldRegister.world_types["A Link to the Past"].option_definitions.items():
             setattr(args, name, {1: option.from_any(option.default)})