refactor: repo maintenance

[Agrendalath]

This:

1. Adds catalog-info.yaml.
2. Updates .gitignore.
3. Removes some leftover code from Python 2.
4. Modernizes building the package.
5. Modernizes running test.
6. Removes unused integration tests.
7. Updates requirements.
8. Adds automatic Python requirement upgrades.
9. Adds the CI workflow to upload the package to PyPI.
10. Improves CI scripts.

[openedx-webhooks]

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[Agrendalath]

@feanil, would you mind reviewing this? I tried to make the git history easy to follow.

[feanil]

Yes, I'll take a look tomorrow.

[openedx-webhooks]

@Agrendalath 🎉 Your pull request was merged! Please take a moment to answer a two question survey so we can improve your experience in the future.

[Agrendalath]

@feanil, the CI fails to create a git tree in this repo (and in the openedx/xblock-google-drive). Are some additional permissions required for the requirements bot?

[feanil]

Yes, there was a team that needed to be added, I've done so and verified that it is fixed.

https://github.com/openedx/xblock-image-explorer/actions/runs/7631295800/job/20788929574