Renaming "./kubestr browse" command to "./kubestr browse pvc"

[shlokc9]

This PR renames the ./kubestr browse command to ./kubestr browse pvc while maintaining the support for ./kubestr browse.

Tested these code changes by executing both the commands on a GKE cluster. Please find the output below;

> ./kubestr browse pvc test-pvc1 -n file-level-restore -v test-snapshotclass
Taking a snapshot
Creating the file browser application.
Forwarding the port.
Port forwarding is ready to get traffic. visit http://localhost:8080/
^CStopping port forward
Cleaning up resources

> ./kubestr browse test-pvc1 -n file-level-restore -v test-snapshotclass
Taking a snapshot
Creating the file browser application.
Forwarding the port.
Port forwarding is ready to get traffic. visit http://localhost:8080/
^CStopping port forward
Cleaning up resources

During cleanup, we clean the placeholder VolumeSnapshot, PVC created from that VolumeSnapshot & the Filebrowser pod.

[bathina2]

minor nits about messaging