Fix Canvas3D/Canvas3DGS async imports

[whitphx]

Description

Closes: #7484

The main fix is 041eb99.
903c81d is a refactoring commit.

In d2ee5df, the undo buttons are disabled in the Gaussian Splatting mode as it's not implemented.

[gradio-pr-bot]

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---

Install Gradio from this PR

pip install https://gradio-builds.s3.amazonaws.com/ece91c97d0e98863f0431d9e09f1f3e4ea47a75f/gradio-4.19.1-py3-none-any.whl

Install Gradio Python Client from this PR

pip install "gradio-client @ git+https://github.com/gradio-app/gradio@ece91c97d0e98863f0431d9e09f1f3e4ea47a75f#subdirectory=client/python"

[gradio-pr-bot]

🦄 change detected

This Pull Request includes changes to the following packages.

Package	Version
@gradio/model3d	patch
gradio	patch

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With the following changelog entry.

Fix Canvas3D/Canvas3DGS async imports

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[pngwn]

Looks great! Thanks for taking care of this @whitphx!