Add nav event creation code from the mapbox-events-android library

[lilykaiser]

Per internal conversation, step 4 in the effort to streamline tracking event ingestion is to refactor event creation code (classes, factories, test, etc...) into the nav SDK and out of mapbox-android-events. Creating this ticket as a placeholder.

[akitchen]

Given the many changes that have happened since this ticket was opened, I don't think we'll be proceeding with this as described. Closing as stale.