[Feature]: Add Localization Distillation for Object Detection (#4758)

* add Localization Distillation for Object Detection https://arxiv.org/abs/2102.12252

* fix lint

* fix lint

* fix lint

* fix lint

* fix lint

* fix config

* add kd detector

* edit loss name

* overide setattr but failed

* move init_detector into init

* seperate ld and gfocal, fix unused param error

* small fix

* small fix

* add test, reload magic function, create kd_loss.py

* del teacher model warnings

* fix reference

* add ignored bbox test fix docstring

* small fix

* docstring fix

* change names

* fix

* fix

* fix test

* fix import

* fix

* docstring fix

* fix

* retest

* add test

* docstring fix