[FancyZones] Implement File Watcher (#8603)

* Implement File Watcher in FancyZones

* Simplify code, address PR comments

* Add check to result of CreateEventW

* Rebase fix

Removed unneeded newline. If we keep it now, VS will just remove it some other time.

src/modules/fancyzones/lib/FileWatcher.h

@@ -0,0 +1,19 @@
+#pragma once
+
+#include "pch.h"
+
+class FileWatcher
+{
+    DWORD m_refreshPeriod;
+    std::wstring m_path;
+    std::optional<FILETIME> m_lastWrite;
+    std::function<void()> m_callback;
+    HANDLE m_abortEvent;
+    std::thread m_thread;
+    
+    std::optional<FILETIME> MyFileTime();
+    void Run();
+public:
+    FileWatcher(const std::wstring& path, std::function<void()> callback, DWORD refreshPeriod = 1000);
+    ~FileWatcher();
+};