[TEST] split base settings in ClusterDiscoveryConfiguration between node and transport client

The default settings that are currently applied to the transport client are about discovery and gateway, modules that are not even loaded on the transport client. We can now remove the local gateway as it's the default one anyway. Also, let's make sure that the discovery setting is only applied to the node, as it is not relevant for transport client.
why the move to transportClientSettings? I doesn't really matter as they should be aligned, but the method is about the node settings, so I think we should keep using nodeSettings?