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/gpu/d3d12/premake5.lua

@@ -7,6 +7,7 @@ project("xenia-gpu-d3d12")
   kind("StaticLib")
   language("C++")
   links({
+    "fmt",
     "xenia-base",
     "xenia-gpu",
     "xenia-ui",
@@ -27,6 +28,7 @@ project("xenia-gpu-d3d12-trace-viewer")
     "aes_128",
     "capstone",
     "dxbc",
+    "fmt",
     "imgui",
     "libavcodec",
     "libavutil",
@@ -71,6 +73,7 @@ project("xenia-gpu-d3d12-trace-dump")
     "aes_128",
     "capstone",
     "dxbc",
+    "fmt",
     "imgui",
     "libavcodec",
     "libavutil",