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.

{
    
    ArithmeticOperationsInAgrFuncVisitor::Data data;
    ArithmeticOperationsInAgrFuncVisitor(data).visit(query);
}
void optimizeAnyFunctions(ASTPtr & query)
{
    RewriteAnyFunctionVisitor::Data data = {};
    RewriteAnyFunctionVisitor(data).visit(query);
}
void optimizeInjectiveFunctionsInsideUniq(ASTPtr & query, const Context & context)
{
    RemoveInjectiveFunctionsVisitor::Data data = {context};
    RemoveInjectiveFunctionsVisitor(data).visit(query);
}
void transformIfStringsIntoEnum(ASTPtr & query)
{
    std::unordered_set<String> function_names = {"if", "transform"};
    std::unordered_set<String> used_as_argument;
    FindUsedFunctionsVisitor::Data used_data{function_names, used_as_argument};
    FindUsedFunctionsVisitor(used_data).visit(query);
    ConvertStringsToEnumVisitor::Data convert_data{used_as_argument};
    ConvertStringsToEnumVisitor(convert_data).visit(query);
}
}
void TreeOptimizer::optimizeIf(ASTPtr & query, Aliases & aliases, bool if_chain_to_multiif)