Enhance Lake of Segments unit test

[mscaldas2012]

Have the Function return the event being posted on EventHubs for the last message processed.
(Since these functions work with JsonElements and JsonObjects instead of POJOS, feel free to covert them into DexEventPayload on the unit test itself, or just use JsonObject )

use the return type to assert appropriately:

Happy Paths should assert summary.current_status is successful and a Process Metadata has been added to the array of processes with appropriate assertion.

Errors should assert summary.current_status, summary.problem and process Metadata has been added to the array of processes with appropriate assertions.