[Bug libstdc++/106749] Implement C++23 library features

[tkaminsk at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106749
Bug 106749 depends on bug 119745, which changed state.

Bug 119745 Summary: [C++23] Implement P2438R2, basic_string::substr() &&
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=119745

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |FIXED