Fix wrong divider position after rotation

Ratating from 270 -> 0 -> 90 keeps wrong "mNonDecorInsets" in the
DisplayLayout of split screen due to not updating insetsState when
insetsChanged. Updtaes to stop house keeping DisplayLayout separately in
split screen component by fetching it from DisplayController directly.

Fix: 285854252
Test: atest WMShellUnitTests
Test: manual by issue steps:
  1) Launch apps to enter split-screen mode
  2) Rotate to 270
  3) Rotate to 0
  4) Rotate to 90
  5) Expect the position of split-tasks is right
Change-Id: Ica32c817ef414f550931a50ec919e3114a075e2c