APIGOV-33307 - enhancements to metrics collection and publishing

[jcollins-axway]

• Create benchmark for before and after changes
  • Update benchmark markdown as changes are made
• Store metrics in cache by information provided during metric report
  • Correlate the metric to the marketplace context when creating the metric for Engage
  • On startup read the existing stored metrics as well as the new stored metric structure
• Remove use of go-metrics and replace with our own metric implementations
  • Metrics only store and update count, min, max and total durations. Calculating average at publish time
• Read all metrics from registry, removing previously used metrics map
  • Clean registry keys at publish time as each metric key will include timestamp for when observation period starts
• Lock on metric collector creation to avoid overwrite of global metric collector or panics writing to same object