Summary of changes:
- Update the charmcraft.yaml file to use base and platforms, only
allowing noble support.
- Update config to default to caracal.
- Update osci.yaml to use the charmcraft 3.x/beta
- Drop non-noble tests
- Update constraints file from -2024.1.txt to -noble.txt
- Add TEST_JUJU3=1 env var to tox.ini to force Juju 3
- Add noble and oracular to charmhelpers
- Add charmbuild .zuul.yaml
Change-Id: I9c6145bedd04395a10f4bac9403bebeaaeff864e
cd1eaa4e96