Upgrade PyO3 (0.23.x -> 0.27.x)

[Qqwy]

Opsqueue's Python library uses PyO3 to generate FFI bindings.

The PyO3 project is evolving fast, with a lot of fixes and improvements happening in the past year.
However, there are some changes to the API / Rust macros, which means that some of the PyO3 annotations will need to be rewritten to be compatible with the newer version.

Steps:

• Blindly try to upgrade and see how much things break
• Open up one or more follow-up issues depending on how much work this turns out to be.