Merge Flow4D model into codebase

[Kin-Zhang]

@jykim94 Check if this pull request is ok, feel free to revise it through new commits on the feature/flow4d branch.

Could you also replace ? to your setting? Specific line in the README:

[Runtime: Around ? hours in ? GPUs.]

[Kin-Zhang]

Do you mind if I uploaded your weight provided to me before into huggingface? so people can directly wget easily? How do you think, Jaeyeul?

[jykim94]

Do you mind if I uploaded your weight provided to me before into huggingface? so people can directly wget easily? How do you think, Jaeyeul?

Did I also provide you the Flow4D weights for Argoverse2? Currently, I don't have available pretrained weights for Argoverse2.
If you upload the Flow4D weights to Hugging Face, that would be great for me!

[Kin-Zhang]

Yes, I think so (let me check) and I can convert to this codebase and send results here later.

Btw, I also add flow4d bib here. Hope you don't mind, let me know if anything wrong with the core code.

And if everything ok, you can approve the review then I will start squash and merge afterward once I check all docs are aligned.

[Kin-Zhang]

Great, I found the weight! And here is the val score (while I will soon have another pull request to update scene flow ground truth things and it will update all methods' scores here)

I will update both the weight and the fixed flow gt demo in the hugging face today.\

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If you find anything incorrect in the core script, feel free to create another pull request! Thanks again for contributing!

[Kin-Zhang]

A link for fixed gt and update all methods scores if interested: #5

[jykim94]

A link for fixed gt and update all methods scores if interested: #5

Got it. Thank you for updating the Flow4D results as well!