Reparent ImeContainer under parent when organized.

If, for whatever reason, the SystemUI process crashed and restarted,
the IME wasn't functional anymore (it would not become visible).

That happened because, after the SystemUI crash, the IME was
unorganized for a while and the framework reparented its surface
under an activity.

With this commit we fix this issue by reparenting the IME under its
parent when it becomes organized again.

Manual Test: Checked that the IME becomes visible after a systemui
             crash.
Test: atest DisplayContentTests
      #testImeContainerIsReparentedUnderParentWhenOrganized
Bug: 224800157
Change-Id: I303baf96c905a9c4b444189b731f63c7d51a11f2

Change-Id: I4d2934516e528bf353395e1759f59612542bdb56