Update metrics package and add metrics in code

[imterryyy]

Currently we don't have a monitoring dashboard of a single Viction node. This dashboard will not only help monitoring metrics, resource spikes and alerts on the fly but also help evaluating our performance updates and bug fixes, to judge if the updates actually brings a performance change or resolves resource leaking overtime, etc.

The first step of implementing a monitoring dashboard like this is put metrics gauges/meters/counters in code where we want to measure. After that, we need to fetch those metrics and index those in a timeseries database like Prometheus or InfluxDB, as data sources for a visualize platform like Grafana.

Checklist:

• Update metrics package with Prometheus and InfluxDB support: Refactor metrics package with Prometheus and InfluxDB support #428
• Apply metrics in code
• Visualize timeseries data on Grafana dashboards

[trinhdn2]

Apply metrics in particular packages

• p2p: Apply metrics in p2p package #433
• rpc: Apply metrics in rpc package #436
• core/txpool: Add metrics in txpool #437
• core/statedb: Apply metrics in core/statedb #439
• core/blockchain: Apply metrics in core/blockchain #440

[trinhdn2]

Visualize timeseries data on Grafana dashboards

[trinhdn2]

Update metrics package with Prometheus and InfluxDB support:

• Refactor metrics package with Prometheus and InfluxDB support #428
• Add and apply InfluxDB related flags #438