Prometheus cluster overview release

Grafana revisions: Prometheus revision 2

Added

• Cluster overview panels for Prometheus

Prometheus release

Grafana revisions: InfluxDB revision 3, Prometheus revision 1

Added

• Dashboard for Prometheus

Changed

• Update metrics version to 0.5.0
• Replace average latency collector with summary collector in example cluster
• Replace average latency panels with summary 99th percentile panels

Fixed

• Example cluster now starts successfully
• Example cluster metrics no more breaks Prometheus metrics collect

InfluxDB configurable policy release

Grafana revisions: InfluxDB revision 2

Added

• Publish dashboard on Grafana official and community built dashboards
• Generate HTTP and space operations traffic for example cluster with luatest

Changed

• Update metrics version to 0.3.0 in experimental cluster
• Rework example Tarantool instance on "cartridge.roles.metrics"
• Rework example Tarantool docker to start multiple instances with luatest
• Make InfluxDB policy configurable
• Documentation improvements and fixes