Add prometheus metrics for Central controllers (#1969)

* add header-only prometheus lib to ext

* rename folder

* Undo rename directory

* prometheus simpleapi included on mac & linux

* wip

* wire up some controller stats

* Get windows building with prometheus

* bsd build flags for prometheus

* Fix multiple network join from environment entrypoint.sh.release (#1961)

* _bond_m guards _bond, not _paths_m (#1965)

* Fix: warning: mutex '_aqm_m' is not held on every path through here [-Wthread-safety-analysis] (#1964)

* Serve prom metrics from /metrics endpoint

* Add prom metrics for Central controller specific things

* reorganize metric initialization

* testing out a labled gauge on Networks

* increment error counter on throw

* Consolidate metrics definitions

Put all metric definitions into node/Metrics.hpp.  Accessed as needed
from there.

* Revert "testing out a labled gauge on Networks"

This reverts commit 499ed6d95e11452019cdf48e32ed4cd878c2705b.

* still blows up but adding to the record for completeness right now

* Fix runtime issues with metrics

* Add metrics files to visual studio project

* Missed an "extern"

* add copyright headers to new files

* Add metrics for sent/received bytes (total)

* put /metrics endpoint behind auth

* sendto returns int on Win32

---------

Co-authored-by: Leonardo Amaral <leleobhz@users.noreply.github.com>
Co-authored-by: Brenton Bostick <bostick@gmail.com>

ext/prometheus-cpp-lite-1.0/core/include/prometheus/benchmark.h

@@ -0,0 +1,72 @@
+#pragma once
+
+#include "prometheus/metric.h"
+#include "prometheus/family.h"
+
+#include <chrono>
+
+namespace prometheus {
+
+  class Benchmark : public Metric {
+
+    #ifndef NDEBUG
+      bool already_started = false;
+    #endif
+
+    std::chrono::time_point<std::chrono::high_resolution_clock>           start_;
+    std::chrono::time_point<std::chrono::high_resolution_clock>::duration elapsed = std::chrono::time_point<std::chrono::high_resolution_clock>::duration::zero(); // elapsed time
+
+  public:
+
+    using Value  = double;
+    using Family = CustomFamily<Benchmark>;
+
+    static const Metric::Type static_type = Metric::Type::Counter;
+
+    Benchmark() : Metric(Metric::Type::Counter) {}
+
+    void start() {
+
+      #ifndef NDEBUG
+        if (already_started)
+          throw std::runtime_error("try to start already started counter");
+        else
+          already_started = true;
+      #endif
+
+      start_ = std::chrono::high_resolution_clock::now();
+
+    }
+
+    void stop() {
+
+      #ifndef NDEBUG
+        if (already_started == false)
+          throw std::runtime_error("try to stop already stoped counter");
+      #endif
+
+      std::chrono::time_point<std::chrono::high_resolution_clock> stop;
+      stop = std::chrono::high_resolution_clock::now();
+      elapsed += stop - start_;
+
+      #ifndef NDEBUG
+        already_started = false;
+      #endif
+
+    }
+
+    double Get() const {
+      return std::chrono::duration_cast<std::chrono::duration<double>>(elapsed).count();
+    }
+
+    virtual ClientMetric Collect() const {
+      ClientMetric metric;
+      metric.counter.value = Get();
+      return metric;
+    }
+
+  };
+
+
+
+}  // namespace prometheus