Add comprehensive gesture recognizer tests

[friedbunny]

Gestures are the primary mode of user interaction with our product, so we need to be sure that they’re doing what we expect. Currently, our gesture tests are inadequate (see #14073) and historically we’ve had bad luck maintaining integration tests (#4794, #13184, etc.), but MGLMapViewDirectionTests in #14082 demonstrates a way that we can mock and test gesture recognizers in unit tests.

/cc @mapbox/maps-ios