[postprocessor] update 'finalize' events

Add 'finalize-error' and 'finalize-success' events that trigger
depending on whether error(s) did or did not happen.

'finalize' itself now always triggers regardless of error status.
(was supposed to have the same behavior as the new 'finalize-success')

gallery_dl/postprocessor/zip.py

@@ -88,7 +88,7 @@ class ZipPP(PostProcessor):
                 if self.delete:
                     util.remove_file(path)
 
-    def finalize(self, pathfmt, status):
+    def finalize(self, pathfmt):
         if self.zfile:
             self.zfile.close()