Create flag for display events logging

Add flag for logging the display event occurred atom. The atom logs display event type and client UIDs. This atom will be used to create a dashboard and metrics in Pitot to be able to detect regressions in the frequency of display events. The event type and the UIDs of the clients receiving the event is also included in the atom to further analyze this information.

Bug: 433479938
Flag: com.android.server.display.feature.flags.enable_logging_for_display_events
Test: atest DisplayServiceTests
Change-Id: I2c67be97bfacaab5a98338e1247df7992727df9d