[$] Change notifications for network filesystems

Steve French led a discussion on change notifications for networkfilesystems in a session at the2022 Linux Storage,Filesystem, Memory-management and BPF Summit (LSFMM). He is part ofthe Samba team and noted that both Windows and macOS clients get notifiedof new and changed files in a shared directory immediately, while on Linux that does not happen. Hewanted to explore what it would take to add that functionality.