Quick fix to gr.utils.validate_url

[abidlabs]

Context: we use gr.utils.validate_url to determine if a string is a URL or a filepath. The logic is quite simple -- we make a GET request to the URL and see if we get a result.

However, some common media hosting sites (e.g. WikiCommons) require a User Agent to be set when making a request -- otherwise, the request is immediately rejected. This fact causes gr.utils.validate_url to fail for these URLs. In addition, since we were checking for a strict 200 response, URLs that redirected to other URLs would fail.

This PR fixes those issues and add tests.

Code to reproduce:

import gradio as gr

with gr.Blocks() as demo:
    gr.Audio("https://upload.wikimedia.org/wikipedia/commons/e/ef/Yellowstone_sound_library_-_Grizzly_Bears_Roar_-_001.mp3")
    
demo.launch()

[github-actions]

All the demos for this PR have been deployed at https://huggingface.co/spaces/gradio-pr-deploys/pr-2659-all-demos

[freddyaboulton]

Thanks @abidlabs !

[freddyaboulton]

Should probably mark as flaky if for whatever reason these urls are unavailable

[abidlabs]

Good catch, thanks @freddyaboulton!