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/cpu/testing/premake5.lua

@@ -4,6 +4,7 @@ include(project_root.."/tools/build")
 test_suite("xenia-cpu-tests", project_root, ".", {
   links = {
     "capstone",
+    "fmt",
     "xenia-base",
     "xenia-core",
     "xenia-cpu",