fix VAE loading issue in train_dreambooth (#7632)
* fixed vae loading issue #7619
* rerun make style && make quality
* bring back model_has_vae and add change \ to / in config_file_name on windows os to make match work
* add missing import platform
* bring back import model_info
* make config_file_name OS independent
* switch to using Path.as_posix() to resolve OS dependence
* improve style
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Co-authored-by: Sayak Paul <spsayakpaul@gmail.com>
Co-authored-by: bssrdf <bssrdf@gmail.com>
Co-authored-by: Dhruv Nair <dhruv.nair@gmail.com>
