* charm-helpers sync for classic charms
* sync from release-tools
* switch to release-specific zosci functional tests
* run focal-ussuri as smoke tests
* remove trusty, xenial, and groovy metadata/tests
* drop py35 and add py39
Depends-On: https://review.opendev.org/c/openstack/charm-cinder/+/814177
Change-Id: If8894bf0150c7fd0a73d70d20753d67efe92c0b8