metrics: pull library and introduce ResettingTimer and InfluxDB reporter (#15910)

* go-metrics: fork library and introduce ResettingTimer and InfluxDB reporter.

* vendor: change nonsense/go-metrics to ethersphere/go-metrics

* go-metrics: add tests. move ResettingTimer logic from reporter to type.

* all, metrics: pull in metrics package in go-ethereum

* metrics/test: make sure metrics are enabled for tests

* metrics: apply gosimple rules

* metrics/exp, internal/debug: init expvar endpoint when starting pprof server

* internal/debug: tiny comment formatting fix

vendor/github.com/influxdata/influxdb/models/consistency.go

@@ -0,0 +1,48 @@
+package models
+
+import (
+	"errors"
+	"strings"
+)
+
+// ConsistencyLevel represent a required replication criteria before a write can
+// be returned as successful.
+//
+// The consistency level is handled in open-source InfluxDB but only applicable to clusters.
+type ConsistencyLevel int
+
+const (
+	// ConsistencyLevelAny allows for hinted handoff, potentially no write happened yet.
+	ConsistencyLevelAny ConsistencyLevel = iota
+
+	// ConsistencyLevelOne requires at least one data node acknowledged a write.
+	ConsistencyLevelOne
+
+	// ConsistencyLevelQuorum requires a quorum of data nodes to acknowledge a write.
+	ConsistencyLevelQuorum
+
+	// ConsistencyLevelAll requires all data nodes to acknowledge a write.
+	ConsistencyLevelAll
+)
+
+var (
+	// ErrInvalidConsistencyLevel is returned when parsing the string version
+	// of a consistency level.
+	ErrInvalidConsistencyLevel = errors.New("invalid consistency level")
+)
+
+// ParseConsistencyLevel converts a consistency level string to the corresponding ConsistencyLevel const.
+func ParseConsistencyLevel(level string) (ConsistencyLevel, error) {
+	switch strings.ToLower(level) {
+	case "any":
+		return ConsistencyLevelAny, nil
+	case "one":
+		return ConsistencyLevelOne, nil
+	case "quorum":
+		return ConsistencyLevelQuorum, nil
+	case "all":
+		return ConsistencyLevelAll, nil
+	default:
+		return 0, ErrInvalidConsistencyLevel
+	}
+}