Make a general plan for python and java release support

[sanjayankur31]

In general, for both Python and Java releases, we should make a plan that says "after a release reaches EOL, we support it for another XYZ months before we drop support".

This is necessary so that in the future, we're able to drop support for EOL core tech in good time. For example, Python 3.6 will be EOL in December 2021, so some time after, we should drop support for it.

This also reduces our maintenance burden since keeping EOL versions functioning is quite a bit of work now, especially if there are major changes.

What we come up with needs to be clearly documented in docs.