Zpx01/dit advanced training

[zpx01]

What does this PR do ?

Adds the following new features to the Diffusion Training Framework:

• FSDP support
• MovieGen 1B/5B/30B Stages 1-3 Training with FSDP + TP/SP + CP
• EC-DiT model (https://arxiv.org/abs/2410.02098)
• Adds mock video data module for mock training across stages 1-3
• Mixed Image-Video Training with THD Packed Sequencing

Collection: diffusion

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