Single oauth button

[Wauplin]

The goal of this PR is to deprecated the use of gr.LogoutButton in favor of a single gr.LoginButton. When the user land on the Space page, the button shows "Sign in with Hugging Face". Once the user is logged in, the button shows "Logout (Wauplin)". This should be cleaner to avoid having a gr.LogoutButton always shown even if the user if not logged in yet.
Logic-wise, I have added a logout_value similar to signed_in_value. I also fixed the JS part to take this into account.

See slack discussion (internal) cc @julien-c.

Demo: https://huggingface.co/spaces/Wauplin/gradio-oauth-demo-pr-7063

When landing on Space:

Once logged in:

[gradio-pr-bot]

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[gradio-pr-bot]

🦄 change detected

This Pull Request includes changes to the following packages.

Package	Version
gradio	minor

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Single oauth button

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[abidlabs]

Thanks @Wauplin for this PR. I've left a couple of small notes above but LGTM

[Wauplin]

Thanks for the review @abidlabs! I've addressed your two comments. Feel free to merge anytime (CI is red but it's related to a permission issue I believe).

[abidlabs]

LGTM, thanks for addressing @Wauplin!