feat(kuma-cp) Reformat some Envoy metrics available in prometheus

[jakubdyszkiewicz]

Summary

Some metrics like this

# TYPE envoy_inbound_192_168_16_2_39081rbac_shadow_denied counter
envoy_inbound_192_168_16_2_39081rbac_shadow_denied{} 0

need some tuning so it will become usable, like this

envoy_rbac_shadow_denied{listener=inbound_192_168_16_2_39081}

I attach current metrics for statsd and prometheus output with the change
example_prometheus_metrics.txt
example_statsd_metrics.txt

[yskopets]

Let's update our Envoy config generator to include . (dot) between listener name and rbac.* suffix

E.g., right now we generate config

      filterChains:
        - filters:
            - name: envoy.filters.network.rbac
              typedConfig:
                '@type': type.googleapis.com/envoy.config.filter.network.rbac.v2.RBAC
                rules:
                  policies:
                    tp-1:
                      permissions:
                      - any: true
                      principals:
                      - authenticated:
                          principalName:
                            exact: spiffe://default/web1
                statPrefix: inbound:192.168.0.1:80

Notice statPrefix: inbound:192.168.0.1:80

It should be statPrefix: inbound:192.168.0.1:80. (notice . (dot) in the end)