Intercepted transition keeps previous distance

This CL ensures that an intercepted transition remembers its previous
swipe distance. This ensures that a transition progress does not
instantly jump in case the user distance changed since it started.

Bug: 290930950
Test: atest DraggableHandlerTest
Flag: com.android.systemui.scene_container
Change-Id: I1395848fd798f9bfb123811ea328039092e0dc59