UI: In XDCR Add Remote Cluster, allow specifying network_type, similar to Capella

In Capella Replication, Add Self-Managed Target, you can specify the "Network Type" option for the target connection information:

Should add similar, except the text would say:

• If an external network been configured for the target cluster, you can choose from the following options.   The optional network_type flag determines whether internal or alternate IP addresses are used when communicating with the target cluster. A value of default enforces the use of internal IP addresses. A value of external enforces the use of alternate IP addresses, whenever possible. For information, see Alternate Addresses.]
   
• The more info link should refer to the Server documentation on creating a reference –  https://docs.couchbase.com/server/current/rest-api/rest-xdcr-create-ref.html