Use config size for DisplayMetrics when override doesn't exist

Use the resource configuration to obtain the display size when
calculation the DisplayMetrics to make sure the app compatibility
overrides can be applied. If there are other overrides such as overrides
for multi-windowing mode, the override value will be used.

Bug: 366337720
Test: Check display size in createAppContext
Test: ResourcesManagerTest
Test: AppConfigurationTests
Flag: EXEMPT bugfix
Change-Id: I08dd396fde38778062b02a17b9ee5b7e175856bc