Use new insets apis for determining the stable/system insets

- The old calls appear to account for the display cutout now which causes
  the landscape/seascape comparison to fail

Bug: 157878422
Test: atest TaskSnapshotControllerTest
Test: TaskSnapshotSurfaceTest
Test: DecorViewTest
Test: Open an app with displaycutout layout shortEdge or always, and
      rotate to landscape in non-gestural mode, and ensure that the
      divider and background are drawn in the right place
Change-Id: Ib51964a76e25f902858aad4e8aeb810dfca2edc0