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/hash.h

@@ -0,0 +1,50 @@
+#pragma once
+
+#include <cstddef>
+#include <functional>
+
+namespace prometheus {
+
+  namespace detail {
+
+    /// \brief Combine a hash value with nothing.
+    /// It's the boundary condition of this serial functions.
+    ///
+    /// \param seed Not effect.
+    inline void hash_combine(std::size_t *) {}
+
+    /// \brief Combine the given hash value with another obeject.
+    ///
+    /// \param seed The given hash value. It's a input/output parameter.
+    /// \param value The object that will be combined with the given hash value.
+    template <typename T>
+    inline void hash_combine(std::size_t *seed, const T &value) {
+      *seed ^= std::hash<T>{}(value) + 0x9e3779b9 + (*seed << 6) + (*seed >> 2);
+    }
+
+    /// \brief Combine the given hash value with another objects. It's a recursion。
+    ///
+    /// \param seed The give hash value. It's a input/output parameter.
+    /// \param value The object that will be combined with the given hash value.
+    /// \param args The objects that will be combined with the given hash value.
+    template <typename T, typename... Types>
+    inline void hash_combine(std::size_t *seed, const T &value,
+                             const Types &...args) {
+      hash_combine(seed, value);
+      hash_combine(seed, args...);
+    }
+
+    /// \brief Compute a hash value of the given args.
+    ///
+    /// \param args The arguments that will be computed hash value.
+    /// \return The hash value of the given args.
+    template <typename... Types>
+    inline std::size_t hash_value(const Types &...args) {
+      std::size_t seed = 0;
+      hash_combine(&seed, args...);
+      return seed;
+    }
+
+  }  // namespace detail
+
+}  // namespace prometheus