Update rejected modes votes only if the display is registered

If an initial display config fails soon after hotplug,
There could be a race condition to update the rejected modes
vote for a display and display being registered.
So fix that by updating the votes by using onDisplayAdded()
and onModeRejected() callbacks.

Bug: 393132034
Test: manual, induce config failure in DRM HWC and test that the
ModeChangeObserver updates the rejected modes votes
Flag: com.android.graphics.surfaceflinger.flags.display_config_error_hal

Change-Id: Icb2ab24567eeca740ab1e997e5e9dcd818b14ed9
Signed-off-by: Manasi Navare <navaremanasi@google.com>