Remove beginLayoutLw and redundant logic about layout

This CL makes every window always ready to layout. DisplayFrames and
InsetsState will be always up-to-date so that we don't need to update
them in beginLayoutLw anymore.

This CL also removes PRIVATE_FLAG_PRESERVE_GEOMETRY which is not used by
anyone.

This can be a step to make the client compute its window frame locally.

Bug: 161810301
Test: atest DisplayPolicyLayoutTests DisplayPolicyTests
            LaunchParamsControllerTests SizeCompatTests
            TaskLaunchParamsModifierTests WallpaperControllerTests
Change-Id: I43a3713246ae67fc4da40eae9bbd6d3c8e26cbb9