core: move to inotify for monitoring the config files

instead of manually polling every second which is not efficient, use inotify.

an added bonus is that inotify is much much faster

src/config/ConfigWatcher.hpp

@@ -0,0 +1,32 @@
+#pragma once
+#include <memory>
+#include <vector>
+#include <string>
+#include <functional>
+
+class CConfigWatcher {
+  public:
+    CConfigWatcher();
+    ~CConfigWatcher();
+
+    struct SConfigWatchEvent {
+        std::string file;
+    };
+
+    int  getInotifyFD();
+    void setWatchList(const std::vector<std::string>& paths);
+    void setOnChange(const std::function<void(const SConfigWatchEvent&)>& fn);
+    void onInotifyEvent();
+
+  private:
+    struct SInotifyWatch {
+        int         wd = -1;
+        std::string file;
+    };
+
+    std::function<void(const SConfigWatchEvent&)> m_watchCallback;
+    std::vector<SInotifyWatch>                    m_watches;
+    int                                           m_inotifyFd = -1;
+};
+
+inline std::unique_ptr<CConfigWatcher> g_pConfigWatcher = std::make_unique<CConfigWatcher>();