[Feature] Support K-Net (#1289)

* knet first commit

* fix import error in knet

* remove kernel update head from decoder head

* [Feature] Add kenerl updation for some decoder heads.

* [Feature] Add kenerl updation for some decoder heads.

* directly use forward_feature && modify other 3 decoder heads

* remover kernel_update attr

* delete unnecessary variables in forward function

* delete kernel update function

* delete kernel update function

* delete kernel_generate_head

* add unit test & comments in knet.py

* add copyright to fix lint error

* modify config names of knet

* rename swin-l 640

* upload models&logs and refactor knet_head.py

* modify docstrings and add some ut

* add url, modify docstring and add loss ut

* modify docstrings