Mk/Uses/python.mk: prepare for python 3.10

[AMDmi3]

Summary

Python versions with 2-digit minor are not currently supported, so fix it in preparation for python 3.10.

Test Plan

Tested in poudriere with python 3.10 as default. Example build log:

https://people.freebsd.org/~amdmi3/py310-libversion.log

[AMDmi3]

Fix min/max version calculation

[antoine]

This is incomplete, PYTHON_REL has to be changed to a 5 digits string too

[AMDmi3]

Switch PYTHON_REL to 5 digits

[AMDmi3]

Fix patch

[AMDmi3]

FYI, complete branch with python 3.10 support is here: https://github.com/AMDmi3/freebsd-ports/tree/python310

[AMDmi3]

• Mk: switch PYTHON_REL to 5 digits to support python 3.10.x
• Mk: add framework support for two digit python minor version

[AMDmi3]

Rebased and updated to latest version split into 3 commits:

• 5 digit PYTHON_REL
• 2 digit minor support
• switch from PYTHON_PORTVERSION to PYTHON_DISTVERSION