Ltx-vid conversion script

[Serenagu525]

Conversion from pytorch weights to jax weights

Downloads ltxv-13b-0.9.7-dev.safetensors from lightricks huggingface, or later loads safetensor in from local path, writes into jax weight ckpt using orbax checkpoint manager. Finally, loaded back into jax transformer through the setup_initial_state method in generate_ltx_video.py. Use transformer state and shardings from there.

Details changes see: https://buganizer.corp.google.com/issues/424190672
Running instructions see: https://buganizer.corp.google.com/issues/424255991

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