Move VVM activation state to device protected storage

VVM activation state is required to suppress legacy voicemail notification. It should not be shown if VVM is activated. Before this CL this information is stored in credential protected storage, and cannot be accessed right after boot. Telephony might have a stale VM count and will attempt to refresh the notification after reboot, which will not be suppressed.

In this CL the activation state is moved to device protected storage. Other account info are sensitive and remain in credential protected storage.

Test: TH

PiperOrigin-RevId: 159492498
Change-Id: I918546cd9874e47c4aa96889aa35916ca6c59890