Fix onUserInteraction not called with 3-button-nav and enableOnBackInvokedCallback=true

Bug: 346943119
Flag: com.android.window.flags.predictive_back_system_anims
Test: atest BackNavigationTests
Test: atest OnBackInvokedCallbackGestureTest
Test: Manual, i.e. verifying in a test app that onUserInteraction is called when pressing back key in 3-button-nav and when enableOnBackInvokedCallback=true
Change-Id: I68d77c921cb7c9c0fc9e5dd587fde0ec679d1d7a