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/examples/use_counters_in_class_example.cpp

@@ -0,0 +1,79 @@
+#include <prometheus/registry.h>
+#include <prometheus/counter.h>
+#include <prometheus/text_serializer.h>
+
+#include <array>
+#include <chrono>
+#include <cstdlib>
+#include <memory>
+#include <string>
+#include <thread>
+#include <iostream>
+
+// use prometheus namespace
+using namespace prometheus;
+
+// for clarity, we deduce the required types
+using IntegerCounter  = Counter<uint64_t>;
+using FloatingCounter = Counter<double>;
+
+using IntegerCounterFamily  = CustomFamily<IntegerCounter>;
+using FloatingCounterFamily = CustomFamily<FloatingCounter>;
+
+// create global registry for use it from our classes
+static Registry globalRegistry;
+
+class MyClass {
+
+  IntegerCounterFamily& counterFamily1 { IntegerCounter::Family::Build(globalRegistry,
+                                         "counter_family_1", "counter for check integer functionality",
+                                         {{"type","integer"}} ) };
+  
+  IntegerCounter& counter11{ counterFamily1.Add({{"number", "1"}}) };
+  IntegerCounter& counter12{ counterFamily1.Add({{"number", "2"}}) };
+  IntegerCounter& counter13{ counterFamily1.Add({{"number", "3"}}) };
+  
+  
+  FloatingCounterFamily& counterFamily2 { FloatingCounter::Family::Build(globalRegistry,
+                                          "counter_family_2", "counter for check floating functionality",
+                                          {{"type","float"}} ) };
+  
+  FloatingCounter& counter21{ counterFamily2.Add({{"number", "1"}}) };
+  FloatingCounter& counter22{ counterFamily2.Add({{"number", "2"}}) };
+  FloatingCounter& counter23{ counterFamily2.Add({{"number", "3"}}) };
+
+public:
+
+  MyClass() = default;
+
+  void member_to_do_something() {
+
+    const int random_value = std::rand();
+
+    if (random_value & 1)  counter11++;
+    if (random_value & 2)  counter12++;
+    if (random_value & 4)  counter13++;
+    if (random_value & 8)  counter21++;
+    if (random_value & 16) counter22++;
+    if (random_value & 32) counter23++;
+
+  }
+
+};
+
+int main() {
+
+  MyClass myClass;
+
+  for (;; ) {
+
+    std::this_thread::sleep_for(std::chrono::seconds(1));
+
+    myClass.member_to_do_something();
+
+    TextSerializer text_serializer;
+    text_serializer.Serialize(std::cout, globalRegistry.Collect());
+
+  }
+}
+