Declare loader run abstract method

Author: elicn

qiling/loader/loader.py

@@ -26,3 +26,7 @@ def save(self) -> Mapping[str, Any]:
 
     def restore(self, saved_state: Mapping[str, Any]):
         self.images = [Image(*img) for img in saved_state['images']]
+
+    # loader main method; derivatives must implement one of their own
+    def run(self) -> None:
+        raise NotImplementedError