update opendb: make polygon operations return new objects
update opendb: make polygon operations return new objects

The-OpenROAD-Project/OpenROAD,The-OpenROAD-Project/OpenROAD,QuantamHD/OpenROAD,QuantamHD/OpenROAD,The-OpenROAD-Project/OpenROAD,The-OpenROAD-Project/OpenROAD,QuantamHD/OpenROAD,The-OpenROAD-Project/OpenROAD,QuantamHD/OpenROAD,QuantamHD/OpenROAD