C++17ification.

C++17ification!

- Filesystem interaction now uses std::filesystem::path.
- Usage of const char*, std::string have been changed to
  std::string_view where appropriate.
- Usage of printf-style functions changed to use fmt.

src/xenia/kernel/xboxkrnl/xboxkrnl_video.cc

@@ -294,7 +294,7 @@ struct BufferScaling {
 };
 void AppendParam(StringBuffer* string_buffer, pointer_t<BufferScaling> param) {
   string_buffer->AppendFormat(
-      "%.8X(scale %dx%d -> %dx%d))", param.guest_address(),
+      "{:08X}(scale {}x{} -> {}x{}))", param.guest_address(),
       uint16_t(param->bb_width), uint16_t(param->bb_height),
       uint16_t(param->fb_width), uint16_t(param->fb_height));
 }