Removed call to setCookie() method from constructor. It should not be...

I've added in the missing associateLead method that interfaces with a method of the same name in the Marketo REST API vendor library. The call to setCookie() was removed from the constructor of the Leads class because when the cookies variable is included in a syncLead call Marketo inexplicably discards all history related to that cookie's tracking ID and you lose all previously recorded anonymous activity associated with it. Instead the associateLead() method must be used after the lead is created to join the tracking value in the _mkto_trk cookie to the lead ID of the newly created lead. When the lead creation and joining of the tracking ID are done separately, the visitor's anonymous activities are preserved and added to the lead's activity log.

Closes #3080224