Old code was removed. Integration tests was adopted to new executor

I.e. we can build queries like

select * from t1 join (select "COLUMN_3" as a, "COLUMN_4" as b from
(values (1, 2), (1, 3))) as t2 on t1.a = t2.a

At the moment it seems that we are enough with two distribution
types: by key (segment) and not by key (any). So, remove all other
types as redundant.

Added a test case with subquery as well.

Now we can traverse only relational nodes in the tree in arbitrary
order.

It is required to traverse the chain of "and" boolean expressions.