Chore: Enable warnings as errors on MSVC (#6456)

* tests: add Sanity test for SplitFilename83

fix test

fix test

* disable `C4715:not all control paths return a value` for nihstro includes

nihstro: no warn

* Chore: Enable warnings as errors on msvc + fix warnings

fixes

some more warnings

clang-format

* more fixes

* Externals: Add target_compile_options `/W0` nihstro-headers and ...

Revert "disable `C4715:not all control paths return a value` for nihstro includes"
This reverts commit 606d79b55d3044b744fb835025b8eb0f4ea5b757.

* src\citra\config.cpp: ReadSetting: simplify type casting

* settings.cpp: Get*Name: remove superflous logs

src/core/file_sys/archive_backend.cpp

@@ -85,6 +85,7 @@ std::u16string Path::AsU16Str() const {
         return {};
     case LowPathType::Invalid:
     case LowPathType::Binary:
+    default:
         // TODO(yuriks): Add assert
         LOG_ERROR(Service_FS, "LowPathType cannot be converted to u16string!");
         return {};