Duplicate Prometheus metrics (for example, name of slowest input queue).

Stale Prometheus metrics are now removed from the metrics endpoint to avoid it growing constantly over time. This includes both metrics with labels when old labels are no longer used and user-status metrics which have since been deleted.

String assignment/clone defeats copy coassignment optimizations.

Performance improvements have been made when coassigning large events in EPL listeners. In particular, this will improve the handling of Cumulocity IoT Measurement events for high-throughput use cases.