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 606d79b55d.

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

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

src/citra_qt/configuration/configuration_shared.h

@@ -6,6 +6,7 @@
 
 #include <QCheckBox>
 #include <QComboBox>
+#include "common/assert.h"
 #include "common/settings.h"
 
 namespace ConfigurationShared {
@@ -91,6 +92,7 @@ Type GetComboboxSetting(int index, const Settings::SwitchableSetting<Type, range
             return static_cast<Type>(index - ConfigurationShared::USE_GLOBAL_OFFSET);
         }
     }
+    UNREACHABLE();
 }
 
 /// Given a Qt widget sets the background color to indicate whether the setting