Productionize nf-polly plugin

[saif-el]

Context

This is a fork of the nf-hello example plugin repository maintained by Nextflow community. We have made the following changes:

• Renamed the classes and configuration in favor of Polly.
• Added a utility reportMetric that can be used by all users running pipelines on Polly to send user-defined metrics to our system.
• Add a nextflow config parameter to control Kinesis stream name, which we will override on infra side itself. User will not set this value.
• The nf-polly plugin will also be automatically enabled for all pipelines on the infra side (separate PR for this in samvaad).
• The tests are failing because the nextflow devs have created a harness that works for only public repositories. We need to come back to this and enable it for our own private use-case.