Cluster demo support updates

Changes include:
- Rework cluster-demo-network-config recipe to have the installed
  service file be a template, allowing the recipe to potentially
  change the target network device easily. A new variable
  AGL_CLUSTER_NET_DEVICE has been added to do so, with a default
  value of eth1. The interface configuration has been moved to a
  helper shell script, cluster-demo-network-conf.sh, with some
  additional logic added to update the interface blacklist in the
  connman configuration. This makes things more generic and allows
  setting up the cluster demo on boards other than H3+KF.
- Update agl-cluster-demo-support feature dependency with new
  agl-weston-remoting feature that replaces agl-gstrecorder.

Bug-AGL: SPEC-3395

Signed-off-by: Scott Murray <scott.murray@konsulko.com>
Change-Id: I9109b8e7782112d5504866f67e6bb5953c79d4a8