vfs_ceph_new: switch to ceph_readdir_r

vfs_ceph_new: switch to ceph_readdir_r

Prefer a safe version of ceph_readdir, where the directory entry struct
is allocated by the caller. Use a dynamic-allocated 'struct dirent'
which is associated with a directory vfs_ceph_fh (optional), which is
allocated on-the-fly upon start of READDIR and released at the end or
CLOSEDIR (or unlikely readdir error).

BUG: https://bugzilla.samba.org/show_bug.cgi?id=15703

Signed-off-by: Shachar Sharon <ssharon@redhat.com>
Reviewed-by: John Mulligan <jmulligan@redhat.com>
Reviewed-by: Anoop C S <anoopcs@samba.org>
Autobuild-User(master): Anoop C S <anoopcs@samba.org>
Autobuild-Date(master): Fri Oct 25 10:29:44 UTC 2024 on atb-devel-224