📈 cdviz-collector: expose prometheus metrics

[davidB]

• expose metrics to prometheus:
  • cdviz_cdevent_total that count the number of events created by sources, or send by sink, with labels:
    • stage: source or sink
    • stage_name: the name of the source or the sink
    • error: empty string if none, else error kind
  • cdviz_processing_duration time between creation by the source with label
    • sink_name: the name of the sink
    • source_name: the name of the source
• show the metrics on grafana dashboard "cdviz-collector activities"
  • count by stage_name
  • increase by stage_name
• add the ServiceMonitor as part of the cdviz-collector chart if not exists

Explore if those metrics could not be extracted by using metrics extracted from tracing-span (see the contrib spanprocessor in otel-collector processor)?