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/inline_strconv_parse.go

@@ -0,0 +1,44 @@
+package models // import "github.com/influxdata/influxdb/models"
+
+import (
+	"reflect"
+	"strconv"
+	"unsafe"
+)
+
+// parseIntBytes is a zero-alloc wrapper around strconv.ParseInt.
+func parseIntBytes(b []byte, base int, bitSize int) (i int64, err error) {
+	s := unsafeBytesToString(b)
+	return strconv.ParseInt(s, base, bitSize)
+}
+
+// parseUintBytes is a zero-alloc wrapper around strconv.ParseUint.
+func parseUintBytes(b []byte, base int, bitSize int) (i uint64, err error) {
+	s := unsafeBytesToString(b)
+	return strconv.ParseUint(s, base, bitSize)
+}
+
+// parseFloatBytes is a zero-alloc wrapper around strconv.ParseFloat.
+func parseFloatBytes(b []byte, bitSize int) (float64, error) {
+	s := unsafeBytesToString(b)
+	return strconv.ParseFloat(s, bitSize)
+}
+
+// parseBoolBytes is a zero-alloc wrapper around strconv.ParseBool.
+func parseBoolBytes(b []byte) (bool, error) {
+	return strconv.ParseBool(unsafeBytesToString(b))
+}
+
+// unsafeBytesToString converts a []byte to a string without a heap allocation.
+//
+// It is unsafe, and is intended to prepare input to short-lived functions
+// that require strings.
+func unsafeBytesToString(in []byte) string {
+	src := *(*reflect.SliceHeader)(unsafe.Pointer(&in))
+	dst := reflect.StringHeader{
+		Data: src.Data,
+		Len:  src.Len,
+	}
+	s := *(*string)(unsafe.Pointer(&dst))
+	return s
+}