refactor: migrate windows specific content.

- move com, dialog and winfct function into new place.
- add testbench for com and winfct.
- dialog now still not working.

testbench/yycc/windows/winfct.cpp

@@ -0,0 +1,48 @@
+#include <gtest/gtest.h>
+#include <yycc.hpp>
+#include <yycc/windows/winfct.hpp>
+
+#define WINFCT ::yycc::windows::winfct
+
+namespace yycctest::windows::winfct {
+#if defined(YYCC_OS_WINDOWS)
+
+    TEST(WindowsWinFct, GetCurrentModule) {
+        auto rv = WINFCT::get_current_module();
+        EXPECT_TRUE(rv.has_value());
+    }
+
+    TEST(WindowsWinFct, GetTempDirectory) {
+        auto rv = WINFCT::get_temp_directory();
+        EXPECT_TRUE(rv.has_value());
+    }
+
+    TEST(WindowsWinFct, GetModuleFileName) {
+        auto handle = WINFCT::get_current_module();
+        ASSERT_TRUE(handle.has_value());
+
+        auto rv = WINFCT::get_module_file_name(handle.value());
+        EXPECT_TRUE(rv.has_value());
+    }
+
+    TEST(WindowsWinFct, IsValidCodePage) {
+        EXPECT_TRUE(WINFCT::is_valid_code_page(437));
+        EXPECT_TRUE(WINFCT::is_valid_code_page(65001));
+
+        EXPECT_FALSE(WINFCT::is_valid_code_page(6161));
+    }
+
+#if defined(YYCC_STL_MSSTL)
+
+    TEST(WindowsWinFct, GetKnownPath) {
+        auto rv = WINFCT::get_known_path(WINFCT::KnownDirectory::LocalAppData);
+        EXPECT_TRUE(rv.has_value());
+    }
+
+#endif
+
+    // YYC MARK:
+    // I can't test CopyFile, MoveFile and DeleteFile.
+
+#endif
+} // namespace yycctest::windows::winfct