Reconfigure displays on ready to apply DisplayWindowSettings

For secondary displays, we apply display settings in RWC#createDisplayContent()
in RAC#setWindowManager() but WMS#reconfigureDisplayLocked() may not take effect since
display was not ready then and reconfigure call will be a no-op.

This CL will reconfigure all displays in WMS#displayReady().

Fixes: 131909551
Test: atest WmTests:DisplayWindowSettingsTests#testDisplayWindowSettingsAppliedOnDisplayReady
Test: manual: 1. adb pull data/system/display_settings.xml
              2. add forcedDensity="XXX" in the row which display
	      name="local:1"
	      3. adb push display_settings.xml data/system
	      4. adb reboot
	      5. Verify if nav bar applies the density change
Change-Id: I21172fbe590da499c633b54bfe53f6e92adb7ee8