Enhance MongoDB connector metrics

This is a follow-up task after applying DBZ-1726 which introduced the common framework and metrics for the MongoDB connector to consider introducing the following enhanced metrics (if applicable):

• secondsBehindMaster (this likely isn't applicable) As indicated by Jiri below, this is published as MilliSecondsBehindSource and is already available
• numberOfDisconnects
• numberOfPrimaryElections (not sure if we can determine this)
• numberOfRolledbackTransactions (applicable?)
• numberofNotWellFormedTransactions (applicable?)
• numberOfLargeTransactions (applicable?)

In DBZ-845, it was asked to consider introducing metrics to track total number of produced messages by topic. While this would not be trivial to work across connector restarts, it may be useful for specific use cases.