[FIX] auth_ldap: replace the deprecated library by one up to date

At 795c7b0a the external dependencies was changed from trying
to import 'ldap' to checking than 'pyldap' package was installed.
The problem is that pyldap is a unmaintained library that should no
longer be used, as explained on the package page:
https://pypi.org/project/pyldap/


"The pyldap fork was merged back into python-ldap, and released as
 python-ldap 3.0.0."

Having pyldap version >= 3.0 installs python-ldap automatically and
will not cause any issue.

The Debian control file package name is adapted to use the latest.

The "ldap" externalm dependency defined in __manifest__.py will cause
pkg_resources.get_distribution() to fail in both case ("python-lap" or
"pyldap"), but the "import" fallback will succeed. For that reason, the
log warning is turned into a log info.

closes odoo/odoo#40249

Note: This library should be replaced by the pure python "ldap3" library.
Signed-off-by: Christophe Monniez (moc) <moc@odoo.com>