* vmalert: remove `vmalert_execution_duration_seconds` metric
The summary for `vmalert_execution_duration_seconds` metric gives no additional
value comparing to `vmalert_iteration_duration_seconds` metric.
* vmalert: update config reload success metric properly
Previously, if there was unsuccessfull attempt to reload config and then
rollback to previous version - the metric remained set to 0.
* vmalert: add Grafana dashboard to overview application metrics
* docker: include vmalert target into list for scraping
* vmalert: extend notifier metrics with addr label
The change adds an `addr` label to metrics for alerts_sent and alerts_send_errors
to identify which exact address is having issues.
The according change was made to vmalert dashboard.
* vmalert: update documentation and docker environment for vmalert's dashboard
Mention Grafana's dashboard in vmalert's README in a new section #Monitoring.
Update docker-compose env to automatically add vmalert's dashboard.
Update docker-compose README with additional info about services.
vmagent replaces Prometheus to perform scrapes and writes
into VictoriaMetrics installation. Prometheus datasource was
dropped, but its config was reused to feed vmagent.
Change also contains simplification in dashboard propagation
to Grafana container by removing excessive json manipulation
steps.
