* fix(server/prometheus): ensure consistent Prometheus registry is used
- there was a conflicting dependency between Metrics initialization and Modules initialization; resolved by separating registry initialization from metrics initialization
- pass in the registry to prevent implicit dependency being broken
- when registering a metric, first attempt to remove any of existing metrics with same name to prevent errors
- to prevent sneaky uses of the implicit registry, replace default import with explicit import so it is clearer when prometheusClient.registry is used
* Add tests for registering metrics
Iain Sproat