(Manual) NVM backup/restore should use a dialog like OTW updates

[AlCalzone]

Is your feature request related to a problem? Please describe. During NVM backup and restore, the Z-Wave network cannot really be interacted with, since the radio is off and any other tasks are queued.

However, the progress is hidden in the small status bar at the top, that can be partially obstructed by the "General actions" dialog.

Describe the solution you'd like At least during manual NVM backup/restore, we should show a progress dialog similar to OTW updates that cannot be closed until the process is done. Probably doesn't hurt during automatic NVM backups too.

Describe alternatives you've considered none

Additional context none