Add support for Python 3.11.0a7.

[icemac]

To run successfully the following changes are required:

• [x] merge of https://github.com/zopefoundation/zodbpickle/pull/64
• [x] recreate the changes made in https://github.com/zopefoundation/zodbpickle/pull/64
• [x] fix of https://github.com/zopefoundation/zodbpickle/pull/64#issuecomment-1025719735 see #67 for the solution
• [x] GHA must provide Python 3.11.0a7.

Fixes #67.

[icemac]

Locally all tests ran fine. Now we have to wait for 3.11.0a7 on GHA.

[dataflake]

@icemac Looks like the only tests that show as failing are old runs from a week ago, everything else succeeds.

[icemac]

This PR is now ready for review.

[icemac]

Thank you for reviewing this PR. 😃