🎨 Various code style / behaviour fixes

- Merged platform sources when possible
- Added URLExecutableSource class
- Moved replaced_by_schema_key to utils/decorators
- Better retryable exception handling in some managers
-  Split SteamHelper into SteamFileHelper and SteamAPIHelper
- Delegated SteamRateLimiter creation to SteamAPIManager init
- Using additional_data for appid in SteamAPIManager
- Added Windows support for Legendary
- Stylistic changed suggested by pylint

src/store/managers/sgdb_manager.py

@@ -1,18 +1,20 @@
-from urllib3.exceptions import SSLError
+from json import JSONDecodeError
+
+from requests.exceptions import HTTPError, SSLError
 
 from src.game import Game
 from src.store.managers.async_manager import AsyncManager
 from src.store.managers.itch_cover_manager import ItchCoverManager
 from src.store.managers.local_cover_manager import LocalCoverManager
 from src.store.managers.steam_api_manager import SteamAPIManager
-from src.utils.steamgriddb import HTTPError, SGDBAuthError, SGDBHelper
+from src.utils.steamgriddb import SGDBAuthError, SGDBHelper
 
 
 class SGDBManager(AsyncManager):
     """Manager in charge of downloading a game's cover from steamgriddb"""
 
     run_after = set((SteamAPIManager, LocalCoverManager, ItchCoverManager))
-    retryable_on = set((HTTPError, SSLError))
+    retryable_on = set((HTTPError, SSLError, ConnectionError, JSONDecodeError))
 
     def manager_logic(self, game: Game, _additional_data: dict) -> None:
         try: