Use new Arcus EventGrid publishing in integration testing

[stijnmoreels]

Is your feature request related to a problem? Please describe.
Currently, we are using the old IEventGridPublisher system in the integration testing where we have a dedicated publisher to publish events. Microsoft has come with their own publishing system which we extended upon in the new Arcus EventGrid package.

Describe the solution you'd like
Use the new Arcus.EventGrid.Core package which extends the new Microsoft EventGrid publishing functionality instead of using our own dedicated publisher.

Additional context
arcus-azure/arcus.eventgrid#243