Enable clipping to viewport when converting coordinates to screen position

[matteblair]

This addresses some uncommon situations where converting a geographic coordinate to a screen position does not have a meaningful result, as described in #2165

This change adds a method to convert coordinates to screen positions "clipped" to the viewport, internally resolving the problematic edge cases.

[matteblair]

To summarize what this looks like for SDK users:

On Android, MapController has a new method that converts a LngLat into a screen position as a PointF and can optionally clip the result to the viewport. The return value is true when the original point is in the current viewport.

public boolean lngLatToScreenPosition(@NonNull final LngLat lngLat, @NonNull final PointF screenPositionOut, boolean clipToViewport)

On iOS, TGMapView has one changed method and one new method (because out-parameters translate to Swift very poorly). First, the signature for viewPositionFromCoordinate now takes a boolean option for clipping to the viewport.

- (CGPoint)viewPositionFromCoordinate:(CLLocationCoordinate2D)coordinate clipToViewport:(BOOL)clip;

There's a separate method to check if a coordinate is in the current viewport.

-(BOOL)viewportContainsCoordinate:(CLLocationCoordinate2D)coordinate;