JSC fix utf8 string creation

[CedricGuillemet]

Fix range error caused by bytes sequence considered invalid. Also, this api was deprecated since c++17.

[Copilot]

Pull request overview

This pull request attempts to fix a range error caused by invalid byte sequences in UTF-8 string creation by replacing the deprecated std::wstring_convert and std::codecvt_utf8_utf16 approach with a simpler implementation using JSStringCreateWithUTF8CString directly. The change removes the UTF-8 to UTF-16 conversion path and instead creates a null-terminated copy of the input string.

Changes:

• Removed <locale> and <codecvt> includes
• Replaced UTF-8 to UTF-16 conversion with direct UTF-8 string creation
• Added comments explaining the rationale for avoiding deprecated APIs

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[Copilot]

The new implementation will incorrectly truncate strings that contain embedded null bytes. When a length is specified, the std::string constructor correctly includes all bytes (including embedded nulls), but JSStringCreateWithUTF8CString treats the input as null-terminated and will stop at the first null byte it encounters.

The previous implementation converted to UTF-16 using JSStringCreateWithCharacters which accepts a length parameter and can handle embedded nulls correctly. While the std::wstring_convert approach is deprecated, a better fix would be to implement manual UTF-8 to UTF-16 conversion (similar to the utf16toUTF8 function in V8InspectorUtils.cpp) and continue using JSStringCreateWithCharacters, or use a non-deprecated UTF-8 to UTF-16 conversion library.