Automatic merge from submit-queue

Explicit namespace from kubeconfig should override in-cluster config

Fixes #43662 

If an explicitly specified namespace is read from a kubeconfig file, we should not fall back to in-cluster config

```release-note
kubectl commands run inside a pod using a kubeconfig file now use the namespace specified in the kubeconfig file, instead of using the pod namespace. If no kubeconfig file is used, or the kubeconfig does not specify a namespace, the pod namespace is still used as a fallback.
```