Add mechanism to clear handlers based on dec

[lurenpluto]

Due to the persistence mechanism of the handler, after dec modifies the handler, if you forget to remove the old handler, there will be residues that will affect the handler mechanism. So consider adding an interface for clearing the handler based on dec granularity. After dec starts or when necessary, you can call the clearing history version once.

[lurenpluto]

Consider removing RouterHandler's local persistence mechanism, at least for Handler.post_object