Add new dialog for warning confirmations

This change updates the Wear warning dialog for when users try
to change permissions for system apps and apps that are targeting
old SDKs.

Because Wear does not have a common dialog yet, I needed to create
a new activity to hold our confirmation view.

Changes:
    - Update logic to show Wear confirmation screen instead of using
      AlertDialog
    - Added WarningConfirmationActivity
    - Change font size for confirmation dialog
    - Make ConfirmationViewHandler support hiding one of the 3 vertical
      buttons
    - rename grant_permissions.xml to more generic confirmation_dialog

BUG: 24132857

Change-Id: Id225e663f0a2cd7b99fb177f780a6a3d0da15214