[Android] Reuse constants to map maneuver types

[yunikkk]

mapbox-java contains strings for maneuver types :
https://github.com/mapbox/mapbox-java/blob/master/services-directions-models/src/main/java/com/mapbox/api/directions/v5/models/StepManeuver.java

We also hardcode this strings in https://github.com/mapbox/mapbox-vision-android-teaser/blob/dev/app/src/main/kotlin/com/mapbox/vision/teaser/utils/RouteUtils.kt.

Let's reuse constants to avoid duplication.