[datafeed] Drop entity deletion handling in the default source / parser This should be handled by specific parser to avoid using "entities.asource". Reimplement it in the ldap parser. Related to #15538288

[sources] Drop 'moved_entities' table handling This was clumsy and could be handled using exturi / cwsource, as the ldap source now does.

[repository] Drop deprecated extid2eid API and friends This will break cwxmlparser based sources. They should be rewritten using a specific parser, based on xml representation or on rqlio. This is harsh but allows a so big cleanup of the code base. Furthermore, it's necessary for asource/extid handling in the entities table which is costly for most app that don't care at all about that... In this cset, delete: * all extid2eid methods * repo._extid_cache handling * [before/after]_entity_insertion source callback * the cwxmlparser and update related tests, notably unittest_datafeed where 'repull' testing has been removed, since it's now handled by the dataimport API and should not be retested there. Related to #15538288 Closes #15538383

[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.