External display limit on ready to enable

SurfaceFlinger needs to receive configuration
for the external display as soon as possible.
This will help to prevent additional mode change.

Change-Id: I18564c3b7e9719e1d951061a95026a794a650557
Bug: 333855343
Test: atest DisplayModeDirectorTest DisplayObserverTest
ExternalDisplayPolicyTest DisplayManagerServiceTest

Change-Id: I4f9266ce13c44d3eb3c74677be87824a8d0125d5