[multi-sources-removal] Drop deleted_entities system table and entities.mtime column
since they were only used by the entities_modified_since api of the
repository which has been dropped. Along with them, the multi-sources-etypes
configuration variable and some sql queries at modification/deletion time of
entities. Bon vent !
Related to #2919300
from yams import schema2sql as y2sql
dbhelper = repo.system_source.dbhelper
rdefdef = schema['CWSource'].rdef('name')
attrtype = y2sql.type_from_constraints(dbhelper, rdefdef.object, rdefdef.constraints).split()[0]
cursor = session.cnxset['system']
sql('UPDATE entities SET asource = source WHERE asource is NULL')
dbhelper.change_col_type(cursor, 'entities', 'asource', attrtype, False)
dbhelper.change_col_type(cursor, 'entities', 'source', attrtype, False)