Playground exclude unavailable packages

[whitphx]

Description

LLM can generate an app that imports Python standard libraries and the LLM-based requirement list generator can add even these package names, which causes the following error.

PythonError: Traceback (most recent call last):
File "/lib/python3.12/site-packages/micropip/_commands/install.py", line 146, in install
raise ValueError(
ValueError: Can't find a pure Python 3 wheel for: 'random'
See: https://pyodide.org/en/stable/usage/faq.html#why-can-t-micropip-find-a-pure-python-wheel-for-a-package

This PR fixes it by checking if the package exists on PyPI and removing unavailable ones from the generated requirements.

Example:
https://87fa2dfb.gradio-website.pages.dev/playground?demo=Hello_World&code=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&reqs=

The prompt that generated the example app above:

Sample app using the random package

[gradio-pr-bot]

🪼 branch checks and previews

•	Name	Status	URL
	Spaces	ready!	Spaces preview
	Website	ready!	Website preview
	Storybook	ready!	Storybook preview
🦄	Changes	detected!	Details

---

Install Gradio from this PR

pip install https://gradio-pypi-previews.s3.amazonaws.com/ac9bf5ec9208b92579f36ee94a247ae3e676c02f/gradio-5.6.0-py3-none-any.whl

Install Gradio Python Client from this PR

pip install "gradio-client @ git+https://github.com/gradio-app/gradio@ac9bf5ec9208b92579f36ee94a247ae3e676c02f#subdirectory=client/python"

Install Gradio JS Client from this PR

npm install https://gradio-npm-previews.s3.amazonaws.com/ac9bf5ec9208b92579f36ee94a247ae3e676c02f/gradio-client-1.8.0.tgz

Use Lite from this PR

<script type="module" src="https://gradio-lite-previews.s3.amazonaws.com/ac9bf5ec9208b92579f36ee94a247ae3e676c02f/dist/lite.js""></script>

[gradio-pr-bot]

🦄 change detected

This Pull Request includes changes to the following packages.

Package	Version
website	minor

• Maintainers can select this checkbox to manually select packages to update.

With the following changelog entry.

Playground exclude unavailable packages

Maintainers or the PR author can modify the PR title to modify this entry.

Something isn't right?

• Maintainers can change the version label to modify the version bump.
• If the bot has failed to detect any changes, or if this pull request needs to update multiple packages to different versions or requires a more comprehensive changelog entry, maintainers can update the changelog file directly.