[FEATURE] Implement pushDownSort for ORDER BY clause with an expression

[Yury-Fridlyand]

Is your feature request related to a problem?

push down isn't called for SortOperator if ORDER BY has an expression.

SELECT int2 FROM calcs ORDER BY abs(int2);

What solution would you like?

Rework pushDownSort to handle expressions too. Probably, they need to be serialized or converted.
Do this for pagination requests too.

What alternatives have you considered?

N/A

Do you have any additional context?