Stardew Valley: Move BaseTest out of __init__.py to comply with future conventions (#4991)

* move everything out of init; fix from imports and some typing errors

* why is there a change in multiserver

* fix some relative shits

worlds/stardew_valley/test/TestFishsanity.py

@@ -1,8 +1,8 @@
 import unittest
 from typing import ClassVar, Set
 
-from . import SVTestBase
 from .assertion import WorldAssertMixin
+from .bases import SVTestBase
 from ..content.feature import fishsanity
 from ..mods.mod_data import ModNames
 from ..options import Fishsanity, ExcludeGingerIsland, Mods, SpecialOrderLocations, Goal, QuestLocations