Hello, there. Run into the problem with DISTINCT expression. It works incorrectly on the main query if it was already applied to one of the subqueries bond with UNION ALL.

**How to reproduce**
Server version: 20.5.4.40. 19.17.6.36 was free of the bug.
Using Datagrip for running queries.
Non-default settings:
```
input_format_defaults_for_omitted_fields: 1
decimal_check_overflow: 0
joined_subquery_requires_alias: 0
```

Consider following query
```
select distinct number
from ((select number from numbers(10)) union all (select number from numbers(20)));
```
It works fine, returning 20 rows as expected.

But if we add distinct to subqueries (it doesn't matter to the first, the second or both)
```
select distinct number
from ((select distinct number from numbers(10)) union all (select distinct number from numbers(20)));
```

Then in 20.5.4.40 we'll see 30 rows with numbers from 0 to 9 duplicated.
However, `count(distinct number)` returns the correct number of rows.

if (!order_by)
        return;
    std::unordered_set<String> group_by_hashes;
    if (auto group_by = select_query->groupBy())
    {
        for (auto & elem : group_by->children)
        {
            auto hash = elem->getTreeHash();
            String key = toString(hash.first) + '_' + toString(hash.second);
            group_by_hashes.insert(key);
        }
    }
    for (auto & child : order_by->children)
    {
        auto * order_by_element = child->as<ASTOrderByElement>();
        auto & ast_func = order_by_element->children[0];
        if (!ast_func->as<ASTFunction>())
            continue;
        MonotonicityCheckVisitor::Data data{tables_with_columns, context, group_by_hashes};
        MonotonicityCheckVisitor(data).visit(ast_func);
        if (!data.isRejected())
        {
            ast_func = data.identifier->clone();
            ast_func->setAlias("");
            if (!data.monotonicity.is_positive)
                order_by_element->direction *= -1;
        }
    }
}
void optimizeRedundantFunctionsInOrderBy(const ASTSelectQuery * select_query, const Context & context)