www/wt: Update to 4.12.1

• Updates Wt to v4.12.1
• Removes unused OPTIONS_GROUP WSTRING (earlier versions using it, somehow it has not been removed)
• Builds using C++20 instead of C++14 (because of new options STDANY STDFS, it's possible to fallback to C++14 when those options are disabled, please let me know and I'll patch it)
• Adds options group WTCPPIMPL for STD* options below
• Adds STDANY option
• Adds STDFS option
• Some other minor fixes

PR: 291346
Reported by: maintainer