Metrics improvements based on recent testing

[andreasohlund]

• Uses DI instead
• All metrics consolidated in a single class
• Cut down on the number of dimensions to avoid performance issues for metrics storage
• No need to separate counters when there is a histogram (you get counters for "free" with them)
• Aligns naming with https://prometheus.io/docs/practices/naming/

[andreasohlund]

I've done some testing and metrics now works fine without overloading Prometheus due to unbounded dimensions