Get default settings without Settings instance

Get the default settings of Dangezone for the current version, without
having to instantiate the Settings class. Note that instantiating the
Settings class also writes the settings to the underlying
`settings.json` file, and there are cases where we don't want this
behavior.

dangerzone/settings.py

@@ -22,7 +22,12 @@ def __init__(self, dangerzone: "DangerzoneCore") -> None:
         self.settings_filename = os.path.join(
             self.dangerzone.appdata_path, "settings.json"
         )
-        self.default_settings: Dict[str, Any] = {
+        self.default_settings: Dict[str, Any] = self.generate_default_settings()
+        self.load()
+
+    @classmethod
+    def generate_default_settings(cls) -> Dict[str, Any]:
+        return {
             "save": True,
             "archive": True,
             "ocr": True,
@@ -38,8 +43,6 @@ def __init__(self, dangerzone: "DangerzoneCore") -> None:
             "updater_errors": 0,
         }
 
-        self.load()
-
     def get(self, key: str) -> Any:
         return self.settings[key]