Support completing interface alternative names

[scop]

Describe the feature/solution

We should support completing interface alternative names in places where we complete interface names. E.g. altname entries in ip link output. https://lwn.net/Articles/794289/

Maintenance (please complete the following information)

• This is a request for new completion
• Link to upstream project query about shipping the completion:

[scop]

#1090 is kindasorta related. (Not a prerequisite, but would be available only when we complete them with ip.)