Classic confinement for juju-helpers

I would like to publish the juju-helpers snap with classic confinement, as with the other juju plugin snaps. It needs to call the juju binary, and can’t just use the juju-client-observe interface to read the juju yaml files. It also needs to call the microk8s.config and kubectl binaries.

ping @jdstrand on this

The requirements are understood and I’ve vetted the publisher. Granting use of classic. This is now live.