There are currently 3 Views interested in handling user's MotionEvents:
- GeckoView which renders web content
- SwipeRefreshLayout which handles pull down to refresh
- BrowserToolbar which can be dynamically hidden

Each of them have different behaviours based on different conditions so I
- removed the coupling of BrowserToolbar and Geckoview from `NestedGeckoView`.
It's `onTouchEventForResult` will now only set behaviour for GeckoView.
- created a new EngineView enum to expose the `PanZoomController` possible
result of how a specific user touch was handled to any components that have a
reference to an instance of EngineView without the need to have
`concept-engine` as a dependency.
- implemented specific behaviour in `SwipeRefreshFeature` for the pull down to
refresh functionality and in the `BrowserToolbarBottomBehavior` for the dynamic
navigation bar functionality.

Mapped PanZoomController's INPUT_RESULT to a new enum in order to not enforce
the need of including geckoview as a dependency in all components interested in
how a user's `MotionEvent` was handled and also because webview doesn't expose
such values so we needed a wrapper for it's handled or not boolean return.