Update pyo3 to 0.22.0

[bschoenmaeckers]

This is the first iteration of the process to update to pyo3 0.22. The first step is to make the current code compile against the new version. In following MR we should feature gate the deprecated gil-refs api's used and implement every method against the Bound wrapper.

[bschoenmaeckers]

I've moved all code using the gil-refs api behind the gil-refs feature so it compiles without it as well now. Please review

[bschoenmaeckers]

I'm not sure about the py-clone feature, should it be enabled or is there a better way?

[JRRudy1]

I am eager to upgrade to PyO3 0.22 but can't until numpy supports it, so let me know if there are any tasks I can take on to help move this forward! Thanks for getting it started :)

[bschoenmaeckers]

Closing in fever of #435