Update logging line to add client_count in DisplayEventCallbackOccurred atom To log number of unique clients that received the event. Bug: 433483856 Flag: com.android.server.display.feature.flags.enable_logging_for_display_events Test: atest DisplayServiceTests Test: atest DisplayFrameworkStatsLoggerTest Change-Id: Ic3214257261aa5cf49515f61c30d894e2e600a1a