Register back action to close the KQS view

As the KQS view is not extending the floating view, we have to
explicitly register the back action to close the KQS view.

Bug: 379778483
Test: open KQS via alt-tab/overflow button and tap the back button
Flag: com.android.launcher3.taskbar_overflow
Change-Id: I140813d1792f0c17aee5f9f8dd9fa3ed8b40ba6c
2 files changed