`--env-from` is not shown in `service describe` and `revision describe`

[rhuss]

When environment variables are specified with --env-from to add from a configmap or a secret, they are correcly inserted into the Knative Service but not shown when using kn service describe or kn revision describe. They should appear on the same level as regular environment variables.

Walkthrough:

$ kubectl create cm testconfig --from-literal=FOO1=BAR1 --from-literal=FOO2=BAR2
configmap/testconfig created

$ kn service create random --image rhuss/random:1.0 --env-from cm:testconfig
Creating service 'random' in namespace 'default':
  0.123s The Route is still working to reflect the latest desired specification.
  0.166s Configuration "random" is waiting for a Revision to become ready.
 12.151s ...
 12.337s Ingress has not yet been reconciled.
 12.626s Ready to serve.
Service 'random' created to latest revision 'random-rdlzd-1' is available at URL:
http://random.default.example.com

$ kubectl exec -it random-rdlzd-1-deployment-75799bf844-4hknx bash
Defaulting container name to user-container.
Use 'kubectl describe pod/random-rdlzd-1-deployment-75799bf844-4hknx -n default' to see all of the containers in this pod.
bash-5.0# env | grep FOO
FOO1=BAR1
FOO2=BAR2

$ kn service describe random --verbose
Name:         random
Namespace:    default
Annotations:  serving.knative.dev/creator=minikube-user
              serving.knative.dev/lastModifier=minikube-user
Age:          5m
URL:          http://random.default.example.com
Cluster:      http://random.default.svc.cluster.local
Revisions:
  100%  @latest (random-rdlzd-1) [1] (5m)
        Image:  rhuss/random:1.0 (pinned to 946b7c)
Conditions:
  OK TYPE                   AGE REASON
  ++ Ready                   5m
  ++ ConfigurationsReady     5m
  ++ RoutesReady             5m

$ kn revision describe random-rdlzd-1 --verbose
Name:                        random-rdlzd-1
Namespace:                   default
Labels:                      serving.knative.dev/configuration=random
                             serving.knative.dev/configurationGeneration=1
                             serving.knative.dev/route=random
                             serving.knative.dev/service=random
Annotations:                 client.knative.dev/user-image=rhuss/random:1.0
                             serving.knative.dev/creator=minikube-user
                             serving.knative.dev/lastPinned=1580285962
Age:                         5m
Image:                       rhuss/random:1.0 (pinned to 946b7c)
Service:                     random
  Configuration Generation:  1
  Latest Created:            true
  Latest Ready:              true
  Traffic:                   100%
Conditions:
  OK TYPE                  AGE REASON
  ++ Ready                  5m
  ++ ContainerHealthy       5m
  ++ ResourcesAvailable     5m
   I Active                46s NoTraffic (The target is not receiving traffic.)

[MIBc]

I can fix it.

[rhuss]

+1, @MIBc going to assign the issue to you