metrics: transition all metrics to using metricsgen generated constructors. (#8488)

## What does this change do?

This pull request completes the change to the `metricsgen` metrics. It adds `go generate` directives to all of the files containing the `Metrics` structs.

Using the outputs of `metricsdiff` between these generated metrics and `master`, we can see that there is not a diff between the two sets of metrics when run locally.
```
[william@sidewinder] tendermint[wb/metrics-gen-transition]:. ◆ ./scripts/metricsgen/metricsdiff/metricsdiff metrics_master metrics_generated
[william@sidewinder] tendermint[wb/metrics-gen-transition]:. ◆
```

This change also adds parsing for a `metrics:` key in a field comment. If a comment line begins with `//metrics:` the rest of the line is interpreted to be the metric help text. Additionally, a bug where lists of labels were not properly quoted in the `metricsgen` rendered output was fixed.

internal/proxy/metrics.gen.go

@@ -0,0 +1,32 @@
+// Code generated by metricsgen. DO NOT EDIT.
+
+package proxy
+
+import (
+	"github.com/go-kit/kit/metrics/discard"
+	prometheus "github.com/go-kit/kit/metrics/prometheus"
+	stdprometheus "github.com/prometheus/client_golang/prometheus"
+)
+
+func PrometheusMetrics(namespace string, labelsAndValues ...string) *Metrics {
+	labels := []string{}
+	for i := 0; i < len(labelsAndValues); i += 2 {
+		labels = append(labels, labelsAndValues[i])
+	}
+	return &Metrics{
+		MethodTiming: prometheus.NewHistogramFrom(stdprometheus.HistogramOpts{
+			Namespace: namespace,
+			Subsystem: MetricsSubsystem,
+			Name:      "method_timing",
+			Help:      "Timing for each ABCI method.",
+
+			Buckets: []float64{.0001, .0004, .002, .009, .02, .1, .65, 2, 6, 25},
+		}, append(labels, "method", "type")).With(labelsAndValues...),
+	}
+}
+
+func NopMetrics() *Metrics {
+	return &Metrics{
+		MethodTiming: discard.NewHistogram(),
+	}
+}

internal/proxy/metrics.go

@@ -2,9 +2,6 @@ package proxy
 
 import (
 	"github.com/go-kit/kit/metrics"
-	"github.com/go-kit/kit/metrics/discard"
-	"github.com/go-kit/kit/metrics/prometheus"
-	stdprometheus "github.com/prometheus/client_golang/prometheus"
 )
 
 const (
@@ -13,35 +10,10 @@ const (
 	MetricsSubsystem = "abci_connection"
 )
 
+//go:generate go run ../../scripts/metricsgen -struct=Metrics
+
 // Metrics contains the prometheus metrics exposed by the proxy package.
 type Metrics struct {
-	MethodTiming metrics.Histogram
-}
-
-// PrometheusMetrics constructs a Metrics instance that collects metrics samples.
-// The resulting metrics will be prefixed with namespace and labeled with the
-// defaultLabelsAndValues. defaultLabelsAndValues must be a list of string pairs
-// where the first of each pair is the label and the second is the value.
-func PrometheusMetrics(namespace string, defaultLabelsAndValues ...string) *Metrics {
-	defaultLabels := []string{}
-	for i := 0; i < len(defaultLabelsAndValues); i += 2 {
-		defaultLabels = append(defaultLabels, defaultLabelsAndValues[i])
-	}
-	return &Metrics{
-		MethodTiming: prometheus.NewHistogramFrom(stdprometheus.HistogramOpts{
-			Namespace: namespace,
-			Subsystem: MetricsSubsystem,
-			Name:      "method_timing",
-			Help:      "ABCI Method Timing",
-			Buckets:   []float64{.0001, .0004, .002, .009, .02, .1, .65, 2, 6, 25},
-		}, append(defaultLabels, []string{"method", "type"}...)).With(defaultLabelsAndValues...),
-	}
-}
-
-// NopMetrics constructs a Metrics instance that discards all samples and is suitable
-// for testing.
-func NopMetrics() *Metrics {
-	return &Metrics{
-		MethodTiming: discard.NewHistogram(),
-	}
+	// Timing for each ABCI method.
+	MethodTiming metrics.Histogram `metrics_bucketsizes:".0001,.0004,.002,.009,.02,.1,.65,2,6,25" metrics_labels:"method, type"`
 }