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/tests/common/file_util.cpp

@@ -0,0 +1,26 @@
+// Copyright 2023 Citra Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#include <array>
+#include <string>
+
+#include <catch2/catch_test_macros.hpp>
+
+#include "common/file_util.h"
+#include "common/string_util.h"
+
+TEST_CASE("SplitFilename83 Sanity", "[common]") {
+    std::string filename = "long_ass_file_name.3ds";
+    std::array<char, 9> short_name;
+    std::array<char, 4> extension;
+
+    FileUtil::SplitFilename83(filename, short_name, extension);
+
+    filename = Common::ToUpper(filename);
+    std::string expected_short_name = filename.substr(0, 6).append("~1");
+    std::string expected_extension = filename.substr(filename.find('.') + 1, 3);
+
+    REQUIRE(memcmp(short_name.data(), expected_short_name.data(), short_name.size()) == 0);
+    REQUIRE(memcmp(extension.data(), expected_extension.data(), extension.size()) == 0);
+}