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.

#include <Core/Settings.h>
#include <Interpreters/TreeOptimizer.h>
#include <Interpreters/OptimizeIfChains.h>
#include <Interpreters/OptimizeIfWithConstantConditionVisitor.h>
#include <Interpreters/ArithmeticOperationsInAgrFuncOptimize.h>
#include <Interpreters/DuplicateDistinctVisitor.h>
#include <Interpreters/DuplicateOrderByVisitor.h>
#include <Interpreters/GroupByFunctionKeysVisitor.h>
#include <Interpreters/AggregateFunctionOfGroupByKeysVisitor.h>
#include <Interpreters/RewriteAnyFunctionVisitor.h>
#include <Interpreters/RemoveInjectiveFunctionsVisitor.h>
#include <Interpreters/RedundantFunctionsInOrderByVisitor.h>
#include <Interpreters/MonotonicityCheckVisitor.h>
#include <Interpreters/ConvertStringsToEnumVisitor.h>
#include <Interpreters/PredicateExpressionsOptimizer.h>
#include <Interpreters/Context.h>
#include <Interpreters/ExternalDictionariesLoader.h>
#include <Parsers/ASTExpressionList.h>
#include <Parsers/ASTFunction.h>
#include <Parsers/ASTLiteral.h>
#include <Parsers/ASTOrderByElement.h>
#include <Parsers/ASTSelectQuery.h>
#include <Parsers/ASTTablesInSelectQuery.h>
#include <Functions/FunctionFactory.h>