improvement(k8s): properly calculate multi Scylla clusters limits
improvement(k8s): properly calculate multi Scylla clusters limits

The target goal is to be able to run multiple Scylla clusters on the
same K8S nodes. It means that we should consider the number of DB
clusters during the calculation of resources we reserve for each of
them.

So, add possibility to get to know the number of tenants and use it
in the limits calculation.

scylladb/scylla-cluster-tests,scylladb/scylla-cluster-tests,scylladb/scylla-cluster-tests,scylladb/scylla-cluster-tests,scylladb/scylla-cluster-tests