feat(events): improve event mapping

[glevco]

This PR changes the way EventManager transmits events. Instead of passing HathorEvents from PubSub directly to the EventStorage and the client WebSocket, it now converts the events to a new EventType enum that has been created.

This allows for decoupling event types between internal events published via PubSub and what we actually want to expose as an interface to our clients, clearing up confusion related to event names and improving proximity to what was described in the original design. This also allowed bringing back events that were previously removed, as they are now separate events mapped from PubSub events.

Acceptance Criteria:

• New EventType enum replaces HathorEvents as the type for BaseEvent
  • LOAD_STARTED event has been brought back, but mapped from existing MANAGER_ON_START event from PubSub.
  • NEW_VERTEX_ACCEPTED is now emitted instead of NETWORK_NEW_TX_ACCEPTED, as it's mapped from it.

[codecov]

Codecov Report

Merging #543 (41670f7) into dev (41670f7) will not change coverage.
The diff coverage is n/a.

❗ Current head 41670f7 differs from pull request most recent head 356fe0b. Consider uploading reports for the commit 356fe0b to get more accurate results

@@           Coverage Diff           @@
##              dev     #543   +/-   ##
=======================================
  Coverage   83.22%   83.22%           
=======================================
  Files         211      211           
  Lines       18673    18673           
  Branches     2593     2593           
=======================================
  Hits        15541    15541           
  Misses       2564     2564           
  Partials      568      568           

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.