`MGLMapboxEvents` automatically recreates its location manager when the host app is reauthorized for Location Services. Added some redundancy to ensure that there is no location manager when either Location Services or Mapbox Metrics is off.
The shared `MGLMapboxEvents` now owns the only instance of `MGLMetricsLocationManager`. It also owns a `MGLMapboxEventsData` object, to which all user-specific data has been relegated. This object can be built up and torn down on the fly, whenever the opt-out preference is toggled. `MGLMapboxEvents` has also given up knowledge of the access token and now queries `MGLAccountManager` for that information, which `MGLMapView` keeps up-to-date.
