Deprecate and ultimately remove local_address and the concept of a "default" interface

[David Ames]

Juju is deprecating unit-get. Network-get juju-info is an invalid attempt to get the "default" binding and it is non-deterministic or if it is it is alphanumberic sorted. The Juju team has asked us to use an explicit binding for all network-get calls. It is their opinion that the charm should not know what the "default" binding is.

* We should deprecate local_address immediately
* Check for all calls to local_address and attempt to replace them with network-get and an explicit binding
* Check for all calls to unit-get and attempt to replace them with network-get and an explicit binding
* As a last resort, if we are not successful with the above we can add an extra binding for a fallback.

[David Ames (thedac)]

Charm helpers deprecation of local_address: https://github.com/juju/charm-helpers/pull/569

[David Ames (thedac)]

WIP first stab at charms.openstack https://review.opendev.org/c/openstack/charms.openstack/+/775463

[OpenStack Infra (hudson-openstack)]

Change abandoned by "David Ames <email address hidden>" on branch: master
Review: https://review.opendev.org/c/openstack/charms.openstack/+/775463
Reason: This was a PoC and not complete.