Archives: Implemented ExtSaveData and SharedExtSaveData

They will be stored in /extsavedata/SDMC and /extsavedata/NAND respectively.
Also redirect some APT_A functions to their APT_U equivalents.
Implemented the gamecoin.dat file in SharedExtSaveData in the PTM module.
Implemented formatting the savegame.
Retake a previous savegame if it exists instead of reporting them as not formatted every time a game is loaded.

src/core/file_sys/archive_romfs.h

@@ -83,6 +83,12 @@ public:
      */
     std::unique_ptr<DirectoryBackend> OpenDirectory(const Path& path) const override;
 
+    ResultCode Open(const Path& path) override {
+        return RESULT_SUCCESS;
+    }
+
+    ResultCode Format(const Path& path) const override;
+
 private:
     friend class File_RomFS;