SF: Remove the vsync method of communicating hotplug errors and enable the hal api path

Flag: com.android.graphics.surfaceflinger.flags.hotplug2
Bug: 303461103
Test: Artificially generated a hotplug error, and manually verified it went through the hal path, and showed the notification
Change-Id: If222f4e81273518d84cdf2bda12602eb4e713ca7