Metrics for Retry policy

[svroonland]

Periodically emit retry metrics from Retry for monitoring and alerting purposes

• Add parameter metricsCollector: Retry.Metrics => UIO[Unit] to Retry.make
• Add metricsInterval: Duration to customize the metrics emission interval
• Emit metrics before end of use of the policy
• Metrics:
  • total number of requests
  • total number of attempts
  • histogram of the number of attempts
• Metrics objects should be summable (including the histogram) to get the total metrics in some period, like in the zio-kinesis Producer