[flexiglass] Rename `BouncerInteractor.hide` to `onImeHidden`.

This better reflects that the view model is notifying the interactor of
a UI event, and the interactor in turn makes a navigational decision.
For more context, see the discussion in ag/24817356.

Bug: 299343836
Test: Unit tests still pass.
Change-Id: If1f1622faef0ad614a7817d3f4315c84eeacd9c0
3 files changed