ansible: update AIX to Python 3.12

[richardlau]

AIX Toolbox now defaults the python3 package to Python 3.12 so we need to adjust our symlinking accordingly.

Refs: #4208

[richardlau]

I've also bumped up the size of:

• /tmp (needed for the script to update from yum to dnf required for aix: fix broken playbook and use dnf #4202).
• /var to avoid having to do multiple runs of the package upgrade task and clearing /var/cache/dnf in between.