Add "ALLOWED_ALWAYS" permGrantState

Add an option for appPermGroupUiInfo objects to be in the "Allowed
always" state, which will ensure the correct label is always shown in
the PermissionAppsFragment, even if there are no foreground only granted
permissions

Fixes: 146431949

Test: Navigate to a permission with foreground and background split
permissions, and deny all "foreground only" apps. The "allowed" label
should still read "allowed always"

Change-Id: I76d52208400df910833826599d5fcad2e389a9f3