Automatic merge from submit-queue
Added warning msg for `kubectl get`
- added warning description regarding terminated pods to `get` long help message
- added printing of warning message in case of `get pods` if there are hidden pods
Fixes#22986 (initiall PR and discussion are here #26417)
## **Output examples:**
### # kubectl get pods
```
NAME READY STATUS RESTARTS AGE
dapi-test-pod1 0/1 Terminating 0 22h
liveness-http 0/1 CrashLoopBackOff 11245 22d
ubuntu1-1206318548-oh9tc 0/1 CrashLoopBackOff 2336 8d
info: 1 completed object(s) was(were) not shown in pods list. Pass --show-all to see all objects.
```
### # kubectl get pods,namespaces
```
NAME READY STATUS RESTARTS AGE
po/dapi-test-pod1 0/1 Terminating 0 22h
po/liveness-http 1/1 Running 11242 22d
po/ubuntu1-1206318548-oh9tc 0/1 CrashLoopBackOff 2335 8d
info: 1 completed object(s) was(were) not shown in pods list. Pass --show-all to see all objects.
NAME STATUS AGE
ns/default Active 89d
ns/kube-system Active 41d
```
### # kubectl get pods -a
```
NAME READY STATUS RESTARTS AGE
busybox 0/1 Error 0 27d
dapi-test-pod1 0/1 Terminating 0 22h
liveness-http 0/1 CrashLoopBackOff 11245 22d
ubuntu1-1206318548-oh9tc 0/1 CrashLoopBackOff 2336 8d
```
### # kubectl get -h
```
Display one or many resources.
Possible resource types include (case insensitive): pods (aka 'po'), services (aka 'svc'), deployments (aka 'deploy'),
replicasets (aka 'rs'), replicationcontrollers (aka 'rc'), nodes (aka 'no'), events (aka 'ev'), limitranges (aka 'limits'),
persistentvolumes (aka 'pv'), persistentvolumeclaims (aka 'pvc'), resourcequotas (aka 'quota'), namespaces (aka 'ns'),
serviceaccounts (aka 'sa'), ingresses (aka 'ing'), horizontalpodautoscalers (aka 'hpa'), daemonsets (aka 'ds'), configmaps (aka 'cm'),
componentstatuses (aka 'cs), endpoints (aka 'ep'), petsets (alpha feature, may be unstable) and secrets.
This command will hide resources that have completed. For instance, pods that are in the Succeeded or Failed phases.
You can see the full results for any resource by providing the '--show-all' flag.
By specifying the output as 'template' and providing a Go template as the value
of the --template flag, you can filter the attributes of the fetched resource(s).
Examples:
.........
````
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