TemplateLB variables for node IP addresses have to
support multiple IP noda address, hence the variables
are in the format of NODE_IPv4_0, NODE_IPv4_1, NODE_IPv4_2, ...
Struct `NodeIPsTemplates` manage the template variables
for multiple nodes that may have different number of IP addresses each.

Add unit and e2e tests on TemplateLBs with multiple IP addresses.

Refs: ovn-org#3328

Signed-off-by: Andrea Panattoni <apanatto@redhat.com>

Make `Test_ETPCluster_NodePort_Service_WithMultipleIPAddresses`
use v4+v6 IP addresses.

Signed-off-by: Andrea Panattoni <apanatto@redhat.com>

The test about NodePort services that are reachable on every
host IP address should reside in the Service suite.

Signed-off-by: Andrea Panattoni <apanatto@redhat.com>