cassandra-4.1 - new branch and code freeze update

[Ekaterina Dimitrova <e....@gmail.com>]

Hi everyone,

As we talked last week - 1st May the code freeze for our next version 4.1
started.
Mick updated us that a new branch was created. cassandra-4.1 - only
bug-fixes that can go to 4.1
Trunk is now for any new development towards 4.2/5.0.
Unfortunately, branching a new version is more involved as we also need CI
infra and upgrade tests paths to be updated.
All details can be found in CASSANDRA-17589
<https://issues.apache.org/jira/browse/CASSANDRA-17589>. Mick did a lot of
work and testing, thank you for your efforts! *Please rebase both cassandra
and cassandra-dtest branches as otherwise you might see a wall of python
tests and in-jvm upgrade tests failing.*
There are still a few tasks to be completed but I believe nothing that
should affect development now. Please let us know if you face any problems!

Butler is new and Brandon will help us bring the new version in there when
he is back tomorrow.

New Jira labels created.
Please review any tickets you have assigned to yourself and ensure the
following:
- Any new development is 4.x or 5.x
- Any bug fixes that can/should go to 4.1 - 4.1.x

Issues that are to be blockers are for now to use the placeholder version
4.1.x and to be marked as critical/blocker. This follows the same
precedence we did for 4.0, though we have not introduced the alpha, beta,
and rc placeholder versions yet. The version 4.1 is only to be used for
resolved issues, and like 4.0, it gets used for all issues resolved in the
4.1-alpha1 to 4.1.0 range.

First cassandra-4.1 Jenkins CI run just kicked in!

Best regards,
Ekaterina