DO NOT MERGE: Add support for extra index url to the pip installer

[bdraco]

Proposed change

needs home-assistant/docker#297

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• Dependency upgrade
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• This PR fixes or closes issue: fixes #
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[frenck]

I think if we rework the base image with the new index (by delivering a default pip configuration) most of this code (and the old code) can actually be removed.

[bdraco]

I think we still need to set something in the base image or add detection for alpine/musl to set the index url

[bdraco]

I guess we have the util to check if it's an official image already so we could tie it to that instead

[frenck]

Going to close this PR for now. It will end up being a different PR all together once our base images have been adjusted (removing most logic, instead of adding new things).

(Also, I'm cleaning up the PRs a bit 🧹 )

../Frenck