We used output list to compare two LogicalProperties before. Since join reorder will change the children order of a join plan and caused output list changed. the two join plan will not equals anymore in memo although they should be. So we must add a project on the new join to keep the LogicalProperties the same.
This PR changes the equals and hashCode funtions of LogicalProperties. use a set of output to compare two LogicalProperties. Then we do not need add the top peoject anymore. This help us keep memo simple and efficient.