Migrate MediaWiki event logging (currently happening via monolog to Kafka) to use the new scalable event intake service.

At this time MediaWiki is logging events using monolog to Kafka via avro. These events are going to a kafka cluster that is solely maintained for this purpose. We want to be able to have MediaWiki logging to the new analytics jumbo cluster and we want that logging to happen via json, not avro per the decision take on the RFC referenced on this ticket: https://phabricator.wikimedia.org/T198256 This is so:

1. we can consolidate all our event logging to happen using the same transport protocol (json via http, not avro)
2. we can decomision the old analytics kafka cluster that is solely maintained for the purpose of receiving these MediaWiki Avro events