Add KIngress short name "king" (#6685)
Add KIngress short name "king" (#6685)

This patch adds `king` as KIngress's short name.

Currently k8s' ingresss has `ing` as short name, but kingress's short name is `kingress` which is still long.

BEFORE:
```
$ kubectl api-resources |grep ingress
ingresses                         ing             extensions                         true         Ingress
ingresses                         kingress        networking.internal.knative.dev    true         Ingress
ingresses                         ing             networking.k8s.io                  true         Ingress
```

AFTER:
```
$ kubectl api-resources |grep ingress
ingresses                         ing             extensions                         true         Ingress
ingresses                         kingress,king   networking.internal.knative.dev    true         Ingress
ingresses                         ing             networking.k8s.io                  true         Ingress
```
knative/serving,knative/serving