Feature: Introduce `ConstTableScan` operator to accelerate table scan with no required columns

[leiysky]

Sometimes, we have to read data from a table while none of the columns will be used in the query.

For example:

• select count(*) from t
• select * from t where exists(select * from t1), none of column from t1 will be used

To accelerate such queries, we can leverage with a new operator ConstTableScan, which will retrieve a dummy column for each row of data.

[leiysky]

cc @sundy-li

[sundy-li]

system.zeros

m1max.local :) select * from zeros limit 5;


┌─zero─┐
│    0 │
│    0 │
│    0 │
│    0 │
│    0 │
└──────┘

5 rows in set. Elapsed: 0.001 sec.