refactor: refactor old IOHelper.

- move pointer left padding macro into single header file.
- move utf8 fopen into single header but not finished.
- add testbench for pointer left padding macro.
- add system pointer size detector according to new migrated features requested.

testbench/yycc/patch/ptr_pad.cpp

@@ -0,0 +1,22 @@
+#include <gtest/gtest.h>
+#include <yycc.hpp>
+#include <yycc/string/op.hpp>
+#include <yycc/patch/ptr_pad.hpp>
+#include <cinttypes>
+
+#define OP ::yycc::string::op
+
+namespace yycctest::patch::ptr_pad {
+
+    TEST(PatchPtrPad, Normal) {
+        auto rv = OP::printf(u8"0x%" PRIXPTR_LPAD PRIXPTR, nullptr);
+        EXPECT_TRUE(rv.has_value());
+
+#if defined(YYCC_PTRSIZE_32)
+        EXPECT_EQ(rv.value(), u8"0x00000000");
+#else
+        EXPECT_EQ(rv.value(), u8"0x0000000000000000");
+#endif
+    }
+
+}