User can get cluster and see that it is ipv6

[nikimanoledaki]

Part of #4255

Description
See the Get Cluster section in the design doc for some notes on implementation.

Scope

• eksctl get cluster returns a field about which ipFamily the cluster is running with -o yaml or -o json

Acceptance Criteria
User Story 1

• As an eksctl user
• Who created a cluster by setting ipFamily to ipv6 in my configuration file
• When I do eksctl get cluster --name <cluster-name> -o yaml
• And when I do eksctl get cluster --name <cluster-name> -o json
• I can see that my cluster has been created with IPv6

User Story 2

• As an eksctl user
• Who created a cluster without setting ipFamily in my configuration file
• When I do eksctl get cluster --name <cluster-name> -o yaml
• And when I do eksctl get cluster --name <cluster-name> -o json
• I can see that my cluster has been created with IPv4 by default

[Himangini]

It should also work for unowned clusters