SystemUI: Split status bar icon controls for vibrate and mute

- Give users the option to disable the Mute icon too as
  Volume icons got split in https://github.com/LineageOS/android_frameworks_base/commit/ca7ceb8aef3e3fb7a899c137efe0c00003499f6d
- Change Volume string to Vibrate to better reflect
  which icon is being disabled.

Change-Id: I1f8a0370f748cf40fc99584188c42bb2a0aa9856