Support Python 3.12

[tarsil]

• Remove support for Python 3.7
• Add support for Python 3.12

@encode/maintainers . If anyone can check this one, it will be greatly appreciated.

This once passed and merged should address this #581 problem as well.

[tarsil]

@Kludex I don't have permissions to bypass this but since 3.7 was removed, this status will be pending and I can't merge. The rest was ok. If someone can bypass this, I would appreciate it.

@tomchristie maybe we can remove the required Python 3.7 to pass the tests and add the 3.11 and 3.12?

[Kludex]

I have permissions. Hold on.

[tarsil]

Thank you @Kludex . I can continue with this and tomorrow we do what we discussed 🙂