Create a Metrics Query Reporting Task

Currently NiFi has metrics reporting tasks which have a specific set of metrics that are sent out to via site-to-site or other protocols. To expand upon this a query based reporting task is proposed to provide users the flexibility to select the types of metrics and the conditions on they should be reported using sql like statements.

 It may be desired that the results of a query are transmitted to any number of targets. The current pattern is to implement this as a Site-to-Site reporting task, but that puts the onus on the user to create a sub-flow with an Input Port for receiving the S2S messages, and it creates additional provenance events for these. A new approach to be considered here is to decouple the results from the destination. Proposed is a RecordSinkService controller service interface, which the query-based reporting task uses to transmit the query results. The configured RecordSinkService implementation would be responsible for the actual transmission of results to the sink. Possible initial implementations include a Site-To-Site RecordSink (for feature parity with the other reporting tasks) and a DatabaseRecordSink (to transmit the query results to an external RDBMS using DBCPConnectionPool).