[rql2sql/test] Ensure test results predictability Without this, test were randomly failing within tox due to different order of solutions.

[rql2sql] Stop generating SQL query from RQL using entities.type This was necessary in the "true multi-sources" time, it's not anymore, while maintaining this index is costly. Related to #15538317

[test] Remove some usages of lgc.testlib

[test] Avoid pytest discovery warnings Having TestServerConfiguration and alike in the test module namespace causes pytest discovery errors, because it thinks it's a test class.

flake8 and all * update some copyright * drop most __docformat__ declaration * fix some flake8 warnings / errors

[schema2sql] Drop deprecated comment

[cnx] Use entity_type instead of entity_metas()['type'] The latter is deprecated in favor of the former which has been introduced on cnx to replace it.

[entity] Reimplement and deprecate entity.cw_metainformation It shouldn't rely anymore on cnx.entity_metas which is itself deprecated, and the cw_metainformation API is similarly not needed anymore, access directly to cwuri / cw_source if needed. Related to #15538288

[repository] Drop type_and_source_from_eid and rename related cache We don't want to handle anymore the entities.asource column so we shouldn't use those anymore. Also rename repository's _type_source_cache into _type_extid_cache as this is what it's containing now. Do similar renaming to the system source API. Related to #15538288

[entity] Stop returning source information in cw_metainformation() We should not need that. It has been introduced to handle things we should not do and probably don't do anymore (e.g. attempting to grasp recursive import of several sites). Related to #15538288.