[VFS] Rewrote STFS to use memory mapping

- Replaced old-style buffer, buffer_length with std::span
- Added STFS and SVOD specific Entry and File classes
- Other smaller improvements

src/xenia/vfs/devices/host_path_file.h

@@ -28,10 +28,10 @@ class HostPathFile : public File {
 
   void Destroy() override;
 
-  X_STATUS ReadSync(void* buffer, size_t buffer_length, size_t byte_offset,
+  X_STATUS ReadSync(std::span<uint8_t> buffer, size_t byte_offset,
                     size_t* out_bytes_read) override;
-  X_STATUS WriteSync(const void* buffer, size_t buffer_length,
-                     size_t byte_offset, size_t* out_bytes_written) override;
+  X_STATUS WriteSync(std::span<const uint8_t> buffer, size_t byte_offset,
+                     size_t* out_bytes_written) override;
   X_STATUS SetLength(size_t length) override;
 
  private: