Make display cutout can produce insets

This CL creates InsetsType and InternalInsetsType for display cutout.
With this CL, WindowInsets.getSystemWindowInsets() can be compatible
with the legacy insets mode.

Fix: 149932355
Test: Open an app which has LAYOUT_IN_DISPLAY_CUTOUT_MODE_ALWAYS
      and hides navigation bar on the display which has double display
      cutout. And check if the app can get the correct result from
      WindowInsets.getSystemWindowInsets().

Change-Id: I381a083d8c30e1678c835eaf5341e941139aa0d7