feat(main): use NetworkTopologyStrategy for SM ks by default

SimpleStrategy is not recommended for the production environments.
It also does not support tablets, which are the way towards scylla
is moving (in some distant time, vnodes might even be deprecated).
Because of that, it also runs into unexpected problems like
#4555.

Because of those reasons, we should switch from keeping SM data in
SimpleStrategy to NetworkTopologyStrategy keyspace by default.

For the default, single local node SM DB cluster, both strategies
result in the single node containing all of SM data. For single DC
SM DB cluster they are also equivalent. On the other hand, for multi
DC SM DB cluster (really not recommended...), NetworkTopologyStrategy
results in keeping replication_factor replicas per DC and not per cluster.
This is theoretically problematic, but such setup is also problematic for
SimpleStrategy, which would still replicate the data in all DCs, so it's
not a new problem. Moreover, this change only defines the default SM
keyspace creation. In case user has some non-default (perhaps not recommended)
SM DB setup, they can always create SM keyspace manually before starting
SM server to configure it to their liking.

Refs #4555

Author: Michal-Leszczynski

pkg/cmd/scylla-manager/db.go

@@ -58,7 +58,7 @@ func createKeyspace(ctx context.Context, c config.Config, logger log.Logger) err
 	return session.Query(mustEvaluateCreateKeyspaceStmt(c)).Exec()
 }
 
-const createKeyspaceStmt = "CREATE KEYSPACE {{.Keyspace}} WITH replication = {'class': 'SimpleStrategy', 'replication_factor': {{.ReplicationFactor}}}"
+const createKeyspaceStmt = "CREATE KEYSPACE {{.Keyspace}} WITH replication = {'class': 'NetworkTopologyStrategy', 'replication_factor': {{.ReplicationFactor}}}"
 
 func mustEvaluateCreateKeyspaceStmt(c config.Config) string {
 	t := template.New("")