GROUP BY with virtual count attribute is invalid for almost all
databases, but it is valid for PostgreSQL, and it had worked until Rails
5.2.2, so it is a regression for Rails 5.2.3 (caused by 311f0011).

I can't find perfectly solution for fixing this for now, but I would not
like to break existing apps, so I decided to allow referencing virtual
count attribute in ORDER BY clause when GROUP BY aggrigation (it partly
revert the effect of 311f0011) to fix the regression #36022.

Fixes #36022.