[libc++][ranges] Addresses:  LWG3719 - Directory iterators should be usable with default sentinel

Addresses:  LWG3719 - Directory iterators should be usable with default sentinel
https://wg21.link/LWG3719

Reviewed By: #libc, Mordante

Differential Revision: https://reviews.llvm.org/D153299

GitOrigin-RevId: 5f8e4315979c266f3610f89d11a48bd43809533d
9 files changed