Initial SSR refactor

[pngwn]

Description

This is the initial part of #8795.

Some light refactoring to make it easier to create both SSR and SPA versions of gradio.

We still need the SPA version so we can fallback to it when node isn't available and also so we can continue to support the embeds.

This PR does the following:

• introduces @gradio/core. This contains mosrt of the inner workings of the gradio frontend, exactly as they were. But instead of being an entire app, these parts are now exported for consumption elsewhere.
• introduces @gradio/spa. This consumes @gradio/core and is the current gradio frontend and what we use to build the actual app currently.
• Refactors the gradio python and gradio lite packages and builds. Instead of @gradio/lite being a special build of @gradio/app (or @gradio/core now). It now has its own dedicated build step + config . All build commands and test commands are contained within the @gradio/lite packages. This has simplified the configs + build processes of both @gradio/spa and @gradio/lite.
• @gradio/app is now empty (i'll add the boilerplate in this PR) but this will be the location of the SSR/ node version of the gradio 'app'. I wanted to use 'app' because this more accurately reflects the nature of its contents.

[gradio-pr-bot]

🪼 branch checks and previews

•	Name	Status	URL
	Spaces	ready!	Spaces preview
	Website	ready!	Website preview
	Storybook	ready!	Storybook preview
🦄	Changes	detecting...

---

Install Gradio from this PR

pip install https://gradio-pypi-previews.s3.amazonaws.com/04a92141dbe233d2d7c650422035290a8cf6931a/gradio-4.41.0-py3-none-any.whl

Install Gradio Python Client from this PR

pip install "gradio-client @ git+https://github.com/gradio-app/gradio@04a92141dbe233d2d7c650422035290a8cf6931a#subdirectory=client/python"

Install Gradio JS Client from this PR

npm install https://gradio-npm-previews.s3.amazonaws.com/04a92141dbe233d2d7c650422035290a8cf6931a/gradio-client-1.5.0.tgz

[abidlabs]

Demos look good to me @pngwn! You can ignore the failing Model3D demo, as that is also failing on main.

Should be good to merge once js tests pass

[whitphx]

Thanks! I really like the split spa/lite packages and build configs.
I just reviewed code around lite and put nit comments but it overall LGTM.

[gradio-pr-bot]

🦄 change detected

This Pull Request includes changes to the following packages.

Package	Version
@gradio/audio	patch
@gradio/build	patch
@gradio/button	patch
@gradio/chatbot	patch
@gradio/core	patch
@gradio/dataframe	patch
@gradio/lite	patch
@gradio/plot	patch
@gradio/spa	patch
@gradio/storybook	patch
@gradio/video	patch
@gradio/wasm	patch
app	patch
gradio	patch
website	patch

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With the following changelog entry.

Initial SSR refactor

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