[Enhance] Get model configs from metafile without installation (#901)

* Support get config from model-index without installing downstream repo

* Rename _get_models_from_package to _get_models_from_config_dir

* adjust priority

* Fix as comment

* Refine exception

* Replace osp.xxx with fileio.xxx

* Refine as comment

* Revert "Replace osp.xxx with fileio.xxx"

This reverts commit 6aed9b2e88f5cf98614772ddbd89ccad22fa7d2f.

* replace fileio with osp

* fix

* Fix as comment