Add vae_roundtrip.py example (#7104)
* Add vae_roundtrip.py example
* Add cuda support to vae_roundtrip
* Move vae_roundtrip.py into research_projects/vae
* Fix channel scaling in vae roundrip and also support taesd.
* Apply ruff --fix for CI gatekeep check
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Co-authored-by: Álvaro Somoza <asomoza@users.noreply.github.com>
