Sandbox letterbox and size compat apps

Sandbox Display#getRealSize and WindowManager
bounds when letterbox or size compat mode are
applied to the configuration. Display uses
this field to provide the sandboxed display
size.

Test: atest WindowConfigurationTests
Test: atest FrameworksMockingCoreTests:android.view.DisplayTests
Test: atest WmTests:SizeCompatTests
Bug: 171386167
Change-Id: I6f78edcd9214b52ab0708e3892bc86ee05bb5b9a