bug(fe): should check the column in distinct on for aggregation query

[st1page]

reproduce

create table t(a int, b int);
explain select distinct on(a,b) count(*) from t;

output

dev=> create table t(a int, b int);
CREATE_TABLE
dev=> explain select distinct on(a,b) count(*) from t;
ERROR:  Panicked when handling the request: insert at index 1 exceeds fixbitset size 1

expected

postgres=# create table t(a int, b int);
explain select distinct on(a,b) count(*) from t;
CREATE TABLE
ERROR:  column "t.a" must appear in the GROUP BY clause or be used in an aggregate function
LINE 1: explain select distinct on(a,b) count(*) from t;
                                   ^