[feature] support JMX metrics

[hpgrahsl]

Similar to what other connectors offer, the MongoDB sink connector should expose JMX metrics in order to be able to monitor the processing of Kafka Connect Sink Records.

Among others, a few useful metrics could be:

• the latest SinkRecord / BsonDocument (per topic?)
• progress i.e. latest offset processed (per topic and parition?)
• total number of processed SinkRecords (per topic?)
• avg time in millis per processed SinkRecord (per topic?)
• etc.