Use QSPanelController in QSContainerImpl

The QSContainerImpl was accessing the QSPanel directly and, in turn,
accessing some of its injected members. By proxying calls through
the controller, we should be able to remove the injected members.

Bug: 168904199
Test: manual
Change-Id: I3aa379f2b64aca12079281096d8134db58031e84
3 files changed