Reduce requirement for creating a Wireguard interface down to just having a name and a private-key.

As a result we will be able to create a Wireguard interface by just running

generate pki wireguard key-pair install interface wg0

Currently, when you are trying to creating such a stub Wireguard interface, you will see the following message which prevents a commit:

"At least one Wireguard Peer is Required"

NOTE1: Current behavior also prevents you from referencing that to-be-created interface in other commands . For example, if you run

generate wireguard client-config clnt  wg0 server router.example.com

You will receive the following error:

Wireguard interface "wg0" does not exist

NOTE2: Some other platforms I tried allows you to create interfaces first, then create peers later. Where creation of interfaces and peers are decoupled, configuration tasks would easier by being able to be broken down in smaller steps
(example screenshot of a reference idea attached - you see a bunch of interfaces are created, but just one peer is created and assigned to one of the interfaces)

NOTE3: I think it would not be necessary to enforce it this way, but we may request the user to put such interface in "disabled" state before committing such peerless interface configurations if desired