Bugfix multiple event listeners with the same name

[filipzeta]

This PR solves issue 2161:
#2161

With this change applied:

...
Add event listener, eventName= TradeEvent
...
Add event listener, eventName= OrderCompleteEvent
...
Add event listener, eventName= TradeEvent
this._eventListeners before: Map(2) { 'TradeEvent' => [ 0 ], 'OrderCompleteEvent' => [ 1 ] }
this._eventCallbacks before: Map(2) {
  0 => [ 'TradeEvent', [Function (anonymous)] ],
  1 => [ 'OrderCompleteEvent', [Function (anonymous)] ]
}
this._eventListeners after: Map(2) { 'TradeEvent' => [ 0, 2 ], 'OrderCompleteEvent' => [ 1 ] }
this._eventCallbacks after: Map(3) {
  0 => [ 'TradeEvent', [Function (anonymous)] ],
  1 => [ 'OrderCompleteEvent', [Function (anonymous)] ],
  2 => [ 'TradeEvent', [Function (anonymous)] ]
}
...

The important bit is that this._eventListeners gets properly concatenated, compared with the logs in the issue 😊

[vercel]

@filipzeta is attempting to deploy a commit to the coral-xyz Team on Vercel.

A member of the Team first needs to authorize it.

[xjcaa]

@armaniferrante could we merge this fix in please?

[Henry-E]

• Fixes a bug
• doesn't change very much code
• tests pass
  It's a merge!