8716 - K8s Proxy Charms

This commit contains the following changes:

- Changes to LCM Charm to configure vca k8s cloud
- K8s installation:
  - Add storageclass to K8s
  - Add k8s to VCA
  - Configure lcm.env to pass k8s cloud name
- Pass k8s cloud name to LCM Charm in charmed
installation
- Pin juju version tu 2.8/stable
- Instal juju after Microk8s in charmed
installation

Change-Id: I62ae50e4f226eba3bbda7c4a310cfe52591de5b4
Signed-off-by: Dominik Fleischmann <dominik.fleischmann@canonical.com>