Added contact properties to Send event action

[danrowden]

Add ability to sync contact data with "Send event" calls, similarly to how the API works.

Uses a dummy "Contact properties" object like the "createOrUpdateContact" action.

Testing

• Added unit tests for new functionality
• Tested end-to-end using the local server
• [If destination is already live] Tested for backward compatibility of destination. Note: New required fields are a breaking change.
• [Segmenters] Tested in the staging environment
• [Segmenters] [If applicable for this change] Tested for regression with Hadron.