[libc++][PSTL] Implement std::replace{,_if,_copy,_copy_if}

Reviewed By: #libc, ldionne

Spies: ldionne, libcxx-commits

Differential Revision: https://reviews.llvm.org/D151841

GitOrigin-RevId: 51131edf83e4d560f19474b8147efc5fc1118295
10 files changed