Goal

• Improve performance of constructing a std::string from std::istreambuf_iterator, e.g. when reading an entire file into a string.

Acceptance criteria

Close upstream bug:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112925

Either the optimization should be committed to the upstream project or the bug should be closed (e.g. because the expected performance benefits were not observed).