Add VAE implementation in PyTorch

[RunFMe]

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[yzhao062]

Thanks for the PR -- I will suggest calling it vae_torch.py other than vae.py to directly overwrite the keras one (we will retire the keras version later

[coveralls]

Pull Request Test Coverage Report for Build 9036157911

Details

• 110 of 117 (94.02%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.02%) to 93.773%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
pyod/models/vae.py	108	115	93.91%
<!--	Total:	110	117	94.02%	-->

Totals
Change from base Build 8309419980:	0.02%
Covered Lines:	9066
Relevant Lines:	9668

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💛 - Coveralls