Make STL swipe distances configurable

This CL changes the userActions map from a Map<UserAction, SceneKey> to
Map<UserAction, UserActionResult>. In addition to the target SceneKey,
the UserActionResult also exposes a UserActionDistance that can be used
to specify the distance of the user action.

This CL makes sure that usages of the previous API still work by making
SceneKey implement UserActionResult.

Bug: 321932826
Test: atest SwipeToSceneTest
Flag: N/A
Change-Id: I6b3832f82a72d3d1dca8cef1c58ccb87b8ec2220