Implement multiple saves import

https://bugs.dolphin-emu.org/issues/12887

Source/Core/DolphinQt/MenuBar.h

@@ -153,6 +153,7 @@ private:
 
   void InstallWAD();
   void ImportWiiSave();
+  void ImportWiiSaves();
   void ExportWiiSaves();
   void CheckNAND();
   void NANDExtractCertificates();
@@ -214,6 +215,7 @@ private:
   QAction* m_extract_certificates;
   std::array<QAction*, 5> m_wii_remotes;
   QAction* m_import_wii_save;
+  QAction* m_import_wii_saves;
   QAction* m_export_wii_saves;
 
   // Emulation