tendermint/issues

# Metricsgen generates metrics.md markdown file

The metricsgen tool parses and reads a metrics struct with various metrics
fields. Currently, the tool uses this data to generate the corresponding prometheus
and no-op constructors for use withint Tendermint. The same data that is parsed
to generate the constructor can trivially be used to generate the [metrics.md]()
documentation file. Autogenerating this file will reduce the toil of keeping this
file up to date and make it less likely for this simple file to become out of date.

- [] metricsgen generates markdown table output using `TemplateData` data
- [] make target added for regenerating this markdown file

# Replace go-kit metrics metricsgen output with standard prometheus types.

Tendermint uses the `go-kit` metrics library to create and register metrics.
Tendermint only uses the standard prometheus implementations of the various
go-kit metrics type. We therefore derive very little benefit from using the `go-kit`
types. It also prevents Tendermint from easily generating two instances of the `nodeImpl`
with metrics for each. This is because `go-kit` under the hood uses the `DefaultRegistery`
from prometheus which is a global object, created and managed by the prometheus
library. Migrating to use just prometheus will allow us to control and insantiate
separate metrics registries for each instance of the `nodeImpl` that is created.

- [] replace go-kit metrics with equivalent standard prometheus types