Add helper methods to create and execute save level dialogs

Changes in this commit :
- Added AreDirtyTemplatesPresent() method to PrefabSystemComponentInterface
- Added ConstructSaveLevelDialog() helper method to create the save level dialog
- Added ExecuteSavePrefabsDialog() helper method to create and execute the save prefabs dialog

Signed-off-by: srikappa-amzn <srikappa@amazon.com>

Code/Editor/CryEditDoc.h

@@ -104,6 +104,12 @@ public: // Create from serialization only
 
     bool CanCloseFrame();
 
+    //! Returns a Modal containing options to save the current level.
+    AZStd::shared_ptr<QDialog> ConstructSaveLevelDialog();
+
+    //! Executes a Modal asking users about their prefabs save preference.
+    void ExecuteSavePrefabsDialog();
+
     enum class FetchPolicy
     {
         DELETE_FOLDER,