[rset] replace entity cw_rset on .limit(inplace=True) will avoid pb if the entity is still referenced by some other entity relations cache. Closes #2065643 Also, drop '_resultset' from some test names on the way (redundant information, we're in ResultSetTC...)

rql('SET X name "BoundaryConstraint" '
    'WHERE X is CWConstraintType, X name "BoundConstraint"')