Raise error if settings from file are not a dict

We verify the loaded settings from files is dict, otherwise we raise a
SettingsError. With that change, we make Pydantic fails a bit faster.

pydantic_settings/sources.py

@@ -1921,6 +1921,10 @@ def _read_files(self, files: PathType | None) -> dict[str, Any]:
                     settings = self._read_file(file_path)
                 except ValueError as e:
                     raise SettingsError(f'Failed to parse settings from {file_path}, {e}')
+                if not isinstance(settings, dict):
+                    raise SettingsError(
+                        f'Failed to parse settings from {file_path}, expecting an object (valid dictionnary)'
+                    )
                 vars.update(settings)
         return vars