cassini-tests: Validate and update run-time integration tests

The container engine, user accounts and K3s test suitesare updated to
ensure that the application workload replicas are distributed over the
nodes using a PodAntiAffinity setting. To simplify the behavior, one
replica is deployed per node, meaning that a baremetal distribution
image now executes one replica instead of three (note this has no
impact on the validation). To support the image 'rolling' upgrade for a
single Pod, the deployment is configured to allow the Pod to be stopped
before the new upgraded Pod is started.

Changelog: other

Signed-off-by: Richard Neill <richard.neill@arm.com>
Signed-off-by: Vikas Katariya <vikas.katariya@arm.com>