Expose metric for "Number of Events Filtered"

MySQL binlog connector currently exposes the ability to filter processing events based on database name (database.whitelist, database.blacklist), by table name (table.whitelist, table.blacklist), and/or by column name (column.blacklist). Currently when a record is filtered based on these criteria, it is exposed by a debug log statement.

Lets improve upon this by exposing the number of events filtered by these configuration values via a new metric named "numberOfFilteredEvents".

Items covered under ticket

• Add new metric.
• Test coverage.
• Update documentation for metric.