[ldap] Stop using entities table in ldap source authentication and parser We may used cwuri for the same purpose, and do one more step towards deletion of entities.extid column. Related to #15538288

[test] Use stdlib unittest in unittest_webconfig.py

[tox] Require ldap3 < 2 for server tests Apparently we are using some constants that got dropped/moved in ldap3 >= 2.0.0 (which came out last week). So stay with version 1.4 until this gets sorted out.