Add interface to suppress "Rerouting..." expression in NavigationView

Nobody has claimed this yet.

**Android API: No dependency**
**Mapbox Navigation SDK version: v1.1.2**

### Steps to trigger behavior
1. Call `MapboxNavigation.setRerouteController` with `null` to disable rerouting
2. Go out side of route

### Expected behavior
"Rerouting..." in `InstructionView` and `ProgressBar` in `SummaryBottomSheet` are not shown.

### Actual behavior
"Rerouting..." in `InstructionView` and `ProgressBar` in `SummaryBottomSheet` are shown.

### Detailed information
For current implementation, this is an expected behaviour ([InstructionView](https://github.com/mapbox/mapbox-navigation-android/blob/v1.1.2/libnavigation-ui/src/main/java/com/mapbox/navigation/ui/instruction/InstructionView.java#L235)/[SummaryBottomSheet](https://github.com/mapbox/mapbox-navigation-android/blob/v1.1.2/libnavigation-ui/src/main/java/com/mapbox/navigation/ui/summary/SummaryBottomSheet.java#L121)).

At the same time, showing those information is a bit confusing because it's not rerouting actually. Instead, if SDK have an interface to suppress those behaviour or to customize the expression (e.g. show "Off route"), it would be more user-friendly.

Review the rerouting behavior in libnavigation-ui/src/main/java/com/mapbox/navigation/ui/instruction/InstructionView.java and SummaryBottomSheet.java, at the linked implementation points. Trace how MapboxNavigation.setRerouteController(null) affects these views, then determine the interface needed to suppress or customize the messages; done means both views no longer show misleading rerouting state when rerouting is disabled.

Written by the indexing model from the issue text.