Rewrite Save Data & Impl Save Data Dialog (#824)

* core: Rewrite PSF parser & add encoder

add .sfo hex pattern to /scripts

* core/fs: allow to mount path as read-only

* common: Add CString wrapper to handle native null-terminated strings

* SaveData: rewrite to implement full functionality

* mock value for SYSTEM_VER

* SavaData: backup features

* SavaData: SaveDataMemory features

* imgui Ref-counted textures

- has a background thread to decode textures

* imgui: rework gamepad navigation

* PSF: fixed psf not using enum class for PSFEntryFmt (was a standard old ugly enum)

- Add null check to CString when itself is used in a nullable field

* SaveDataDialog implementation

- Fix Mounting/Unmounting check of SaveInstance

src/common/io_file.h

@@ -219,4 +219,6 @@ private:
     uintptr_t file_mapping = 0;
 };
 
+u64 GetDirectorySize(const std::filesystem::path& path);
+
 } // namespace Common::FS