Notify all camera listeners on open/close.

Since there is a close delay, a new open can overwrite a camera
listener, and the camera compat might not be undone for the
original close.

Remove the return variable for camera opened, as the camera
monitor should not track the state of its listeners.

Flag: com.android.window.flags.camera_compat_for_freeform
Test: atest WmTests:CameraStateMonitorTests
Fixes: 347882285
Change-Id: I65d80904aabde3507ac2ac2c6d370a7ee2dd800a