VFS Regression and Accuracy Fixes (#776)

* Regression and Mode Fixes

* Review Fixes

* string_view correction

* Add operator& for FileSys::Mode

* Return std::string from SanitizePath

* Farming Simulator Fix

* Use != With mode operator&

src/core/file_sys/mode.h

@@ -11,7 +11,13 @@ namespace FileSys {
 enum class Mode : u32 {
     Read = 1,
     Write = 2,
+    ReadWrite = 3,
     Append = 4,
+    WriteAppend = 6,
 };
 
+inline u32 operator&(Mode lhs, Mode rhs) {
+    return static_cast<u32>(lhs) & static_cast<u32>(rhs);
+}
+
 } // namespace FileSys