Add IP family validation for IPPool and ExternalIPPool

[luolanzone]

Describe the problem/challenge you have

IPPool and ExternalIPPool shared the same validations, but it doesn't check cluster's IP family, which means following cases would happen:

An IPv4 ExternalIPPool/IPPool in an IPv6-only cluster
An IPv6 ExternalIPPool/IPPool in an IPv4-only cluster

Describe the solution you'd like

The validation should check the cluster's IP family configuration (IPv4Enabled/IPv6Enabled) and reject ExternalIPPools that don't match any enabled IP family. This would provide better user experience by failing fast at creation time rather than silently accepting invalid configurations.

[luolanzone]

cc @antoninbas @tnqn in case you have any comments. Thanks.