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/string_util.h

@@ -10,7 +10,9 @@
 namespace Common {
 
 /// Make a string lowercase
-[[nodiscard]] std::string ToLower(std::string str);
+[[nodiscard]] std::string ToLower(std::string_view str);
+
+void ToLowerInPlace(std::string& str);
 
 std::vector<std::string> SplitString(const std::string& str, char delimiter);