Rename ShapeGridInteractor and ShapeGridRepository

Since when applying we set both shape and grid at the same time. It
makes more sense to have one interactor and repo to handle it in one
call.

Test: Refactor. Make sure it builds and runs.
Bug: 362237825
Flag: com.android.systemui.shared.new_customization_picker_ui
Change-Id: I46ea9aa56c251d7eee943bee70be727192ceba89