🎨 Made manager attributes more flexible

Changed run_after, retryable_on and continue_on to be type Container.
We don't need them to be sets.

The performance gain of sets over small tuples is nonexistant
for in checks and the  syntax is more verbose.

src/store/managers/online_cover_manager.py

@@ -13,8 +13,8 @@ from src.utils.save_cover import resize_cover, save_cover
 class OnlineCoverManager(Manager):
     """Manager that downloads game covers from URLs"""
 
-    run_after = set((LocalCoverManager,))
-    retryable_on = set((HTTPError, SSLError))
+    run_after = (LocalCoverManager,)
+    retryable_on = (HTTPError, SSLError)
 
     def manager_logic(self, game: Game, additional_data: dict) -> None:
         # Ensure that we have a cover to download