Update python version in client image

[maxnoe]

From a discussion on mattermost:

3.9 is being dropped by many third party packages, so using the official client image as basis becomes harder and limiting.

Would be great, if the python version in the client image could be updated to e.g. 3.12.

@dchristidis voiced some concerns:

For example: there’s no configuration for alternatives. As such, python3 will always point to 3.9. Surely not a blocker, but something to be aware of.

and

One more thing that I thought of later: for vendors that target EL9, it definitely doesn’t ‘ship’ Python 3.12. So with dependencies like GFAL and cx_Oracle, we can no longer use their RPM packages and are moving away from what is the supported environment.

[bari12]

This is not only true for the client image, but also server/daemon. Officially python 3.9 is not in EOL until October this year.

We should evaluate that change, not only for the clients, but also for server and daemons. Perhaps by providing an alternative container for these which we can use for testing?