🎨 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/manager.py

@@ -64,7 +64,7 @@ class Manager:
         """Execute the manager logic and handle its errors by reporting them or retrying"""
         try:
             self.manager_logic(game, additional_data)
-        except Exception as error:
+        except Exception as error:  # pylint: disable=broad-exception-caught
             logging_args = (
                 type(error).__name__,
                 self.name,