[server] change order of entities table modification vs entity creation/deletion In order to have a foreign key referencing the entities table, the insertion into entities must happen first, and the deletion must happen last. For the deletion case, this means we need to: 1. delete all relations (cascade) 2. delete the entities themselves 3. delete the corresponding lines from the entities table This means the _delete_info{,_multi} methods can't keep doing 1 and 3. Thankfully the "public" delete_info method appears to be unused, so drop it. Related to #4846892.

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raise NotImplementedError("Cannot migrate such an old version. Use intermediate Cubiweb version (try 3.16.x)")