Add calls to the EventEmitter on Trace fetching (all events, except STOPPED_INFO)

[danielbdias]

On this task, we should handle the following examples:

Stage	Event Type	Description
Trace	POLLING_START	Starting the trace polling process
Trace	POLLING_ITERATION_INFO	A polling iteration has been executed,# of spans - iteration # - reason of next iteration
Trace	POLLING_SUCCESS	The polling strategy has succeeded in fetching the trace from the Data Store
Trace	POLLING_ERROR	The polling strategy has failed to fetch the trace
Trace	FETCHING_START	Starting the trace fetching process
Trace	FETCHING_SUCCESS	The trace was successfully processed by the backend
Trace	FETCHING_ERROR	The trace was not able to be fetched