P3981 R2 Better return types in std::inplace_vector and std::exception_ptr_cast

[wg21bot]

P3981R0 Better return types in std::inplace_vector and std::exception_ptr_cast (Barry Revzin, Jonathan Wakely, Tomasz Kamiński)

[wg21bot]

P3981R1 Better return types in std::inplace_vector and std::exception_ptr_cast (Barry Revzin, Jonathan Wakely, Tomasz Kamiński)

[wg21bot]

P3981R2 Better return types in std::inplace_vector and std::exception_ptr_cast (Barry Revzin, Jonathan Wakely, Tomasz Kamiński)