* make each blob of the packed blob be updated separately in the ModelUpdate

* make blob descs in regst be consistent in bw->md_diff_acc->shared_md_diff_add->md_update->fw

* copy lbi2blob_descs from model

* add shared_model_diff_add kernel

* refine model_update actor and kernel

* rm useless TODO

* add shared_model_diff_add kernel

* refine code


Former-commit-id: 11408363