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 (!select_query->join())
        return;
    const auto * table_join = select_query->join()->table_join->as<ASTTableJoin>();
    if (!(table_join && table_join->using_expression_list))
        return;
    ASTs & expression_list = table_join->using_expression_list->children;
    ASTs uniq_expressions_list;
    std::set<String> expressions_names;
    for (const auto & expression : expression_list)
    {
        auto expression_name = expression->getAliasOrColumnName();
        if (expressions_names.find(expression_name) == expressions_names.end())
        {
            uniq_expressions_list.push_back(expression);
            expressions_names.insert(expression_name);
        }
    }
    if (uniq_expressions_list.size() < expression_list.size())
        expression_list = uniq_expressions_list;
}
void optimizeAggregationFunctions(ASTPtr & query)