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

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106749
Bug 106749 depends on bug 111667, which changed state.

Bug 111667 Summary: [C++23] Implement P1132R8, out_ptr - a scalable output pointer abstraction
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111667

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