Dispatches GPS events to the user's callback module.
The callback module is read from config.callback and must implement
LocationSimulator.Event.
Behaviour
{:ok, config}— updates pipeline config and increments success counter{:error, _}— increments failed counter, worker continues{:stop, _}— setshalted: trueto stop worker
The user can pass callback: MyModule in options, or rely on the
default callback module (taken from config).