3.x: ignore zero-token DCs on RF satisfaction check

[dkropachev]

On tokenMap compute driver assess rf and number of replicas in dc and throw following WARNING if there is not enough replicas:

WARN  [cluster1-worker-2] 2025-03-05 13:16:46,205 ReplicationStategy.java:204 - Error while computing token map for keyspace keyspace1 with datacenter eu-northscylla_node_north: could not achieve replication factor 3 (found 0 replicas only), check your keyspace replication settings.

We need to tune it to ignore DCs that have only zero-token nodes.