[Feature] add config new feature

[HAOCHENYE]

Motivation

References config cross-library

for example, reference mmdet config file in mmtracking:

demo_config.py

_base_ = 'mmdet::faster_rcnn/faster_rcnn_r50_fpn_1x_coco.py'

Build the mmdet model from config.

from mmengine import Config
from mmengine import MODELS, Registry

TRACKING_MODELS = Registry('mmtrack', MODELS)

cfg = Config.fromfile('demo_config.py')
model  = TRACKING_MODELS.build(cfg.model)

Get config and get model cross-library

from mmengine import get_model, get_config

model = get_model('mmdet::faster_rcnn/faster_rcnn_r50_fpn_1x_coco.py')
cfg = get_config('mmpose::face/2d_kpt_sview_rgb_img/deeppose/wflw/res50_wflw_256x256.py')