[ldapfeed] make code compatible with ldap3>=2
* Some constants have been renamed.
* Directly bind when data-cnx-dn/data-cnx-password are provided, some servers,
including ours require this.
* Use raise_exceptions=True to avoid ignored ldap errors
* raise in case of failed anonymous bind
* do not search for "dn" attribute because this raise an "invalid attribute"
with new ldap3 versions
* Password is now returned as bytes, so no longer need to encode them before crypt.
* modification_date is now returned as a datetime object
Co-Authored-By: Philippe Pepiot <philippe.pepiot@logilab.fr>
Closes #16073071