* update:
- charmcraft.yaml for v3
- tox.ini to use py3.12 by default
- test-requirements.in to use zaza for juju3
- update test bundles to work with charmcraft v3
* generate:
- merged-requirements-py312.txt
- test-requirements-py312.txt
* add:
- update-requirements env to tox.ini and src/tox.ini
Change-Id: Ic90520908b7ea5b979881c75136271af6614a94c
Signed-off-by: Munir Siddiqui <munir.siddiqui@canonical.com>