* Metrics: remove unused metrics
Metric `M_Grafana_Version` is not used anywhere, nor the mentioned
`M_Grafana_Build_Version`. Seems to be an artefact?
* Metrics: make the naming consistent
* Metrics: add comments to exported vars
* Metrics: use proper naming
Fixes#18110
Since we do not like some of the default golint rules,
this commit proposes to use https://github.com/mgechev/revive.
And potential revive speed-up should't hurt :).
Right now, presented config (./conf/revive.toml) is permissive,
we might improve it over time however. Fixes for found revive
issues in the code are very limited so it wouldn't be large to review.
Also in this commit:
* Add annotations for makefile commands and declare phony targets
* Rename "gometalinter" script and CI command to "lint"
since we are doing there a bit more then using gometalinter package
* Add Makefile rules to .editorconfig
* Documentation which mentioned "golint" replaced with revive
Fixes#16109
Ref #16160
