Unifying data processing script for Wan M-bridge and Automodel (#83)

* workable code prepare_dataset_wan.py - tested matching automodel's preprocess_resize.py; encode-decode verified

* fix linr

* change location of prepare_dataset_wan.py

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Co-authored-by: Huy Vu2 <huvu@login-eos02.eos.clusters.nvidia.com>

Author: huvunvidia