[FancyZones] Refactor/improve saving JSON files (#8947)

* Divide SaveFancyZonesData into two functions

* Removed unused function, continued refactoring

* Use SaveAppZoneHistory in some places

* Revert "Use SaveAppZoneHistory in some places"

This reverts commit 74a4a1e467.

* Only save files if the contents are about to be changed

* Restore FileWatcher

src/modules/fancyzones/lib/FancyZonesData.h

@@ -85,6 +85,8 @@ public:
 
     void LoadFancyZonesData();
     void SaveFancyZonesData() const;
+    void SaveZoneSettings() const;
+    void SaveAppZoneHistory() const;
 
 private:
 #if defined(UNIT_TESTS)