Move components to an optional `gradio[components]` extra so core Gradio is lightweight

We want Gradio to be a lightweight alternative to FastAPI for any app, including gr.Server apps that don't use Gradio's built-in components.

Proposal

• Make the base pip install gradio minimal: server, queue, client, and gr.Server
• Move the UI components and their heavy dependencies (e.g. image/audio/video processing, pandas) to an optional extra: pip install gradio[components]
• Show a clear error message when a component is used without the extra installed

Considerations

• Migration path and messaging for existing users (this is a breaking change for Gradio 7)
• Spaces' default Gradio SDK install should probably include the extra
• Measure install size and import time before and after