Add enum value for tracking whether there are screen wakelocks to DisplaySwitchLatencyTracked

This CL adds a new enum value to the SystemUI display switch atom
for tracking whether there are screen wakelocks that prevent the screen from turning off.

Bug: 401532886
Flag: EXEMPT updating proto enum
Test: presubmit
Change-Id: I8329f1d95126415906671817ad0fc9be576edb56