cubicweb #2919300 Drop all old multi-source option [validation pending]

After a few years experimenting "true" multi-sources, we're now moving to "copy-based" source à la datafeed.

As pyro and zmq sources have no more known customers and the related code is in the way of future refactoring of cubicweb's core, we decided to drop support for those sources without backward compatibility.

done in3.19.0
load left0.000
closed by#032825bbacab [multi-sources-removal] Drop entities.source column
patch[multi-sources-removal] Drop entities.source column [applied][multi-sources-removal] Drop no more used federated ('true') multi-sources related code [applied][multi-sources-removal] Turn ConnectionsSet into simpler ConnectionWrapper [applied][multi-sources-removal] Drop cnxset_freed from source interface [applied][multi-sources-removal] Simplify ConnectionsSet internal structures and public methods [applied][multi-sources-removal] Drop foreid argument of repo.get_option_value [applied][multi-sources-removal] Kill repo.sources [applied][multi-sources-removal] Drop no more necessary scleanup (source cleanup) argument [applied][multi-sources-removal] drop source location search on glob_*[entity|relation] methods [applied][multi-sources-removal] Drop (dont_)cross relation related code [applied][multi-sources-removal] Simplify repo.delete_info_multi arguments, uri is no more used [applied][multi-sources-removal] Drop deleted_entities system table and entities.mtime column [applied][multi-sources-removal] drop repository entities_modified_since public api [applied][multi-sources-removal] Drop the "true" multi-sources planner [applied][multi-sources-removal] Move cw.server.sources.ConnectionWrapper where it belongs [applied][multi-sources-removal] Drop cw.server.sources.extlite [applied][multi-sources-removal] Drop pyrorql and zmqrql sources [applied]