**Describe the issue**
Can't insert `String` data to column with `LowCardinality` type.

Starting from 21.1 this query fails

**How to reproduce**
```sql
CREATE TABLE default.lc_test
(   
    `id` LowCardinality(String)
)
ENGINE = MergeTree
PARTITION BY tuple()
ORDER BY id;

Ok.
0 rows in set. Elapsed: 0.003 sec.


insert into lc_test values (toString('a'));
Exception on client:
Code: 49. DB::Exception: Bad cast from type DB::ColumnString to DB::ColumnLowCardinality: data for INSERT was parsed from query

```

**Additional context**
related to issue https://github.com/DarkWanderer/ClickHouse.Client/issues/66

version 20.12 ok
{
        for (size_t i = 0; i < ast->children.size(); ++i)
            if (std::find(dont_visit_children.begin(), dont_visit_children.end(), i) == dont_visit_children.end())
                visit(ast->children[i], force_nullable[i]);
    }
    void visit(ASTFunction & function, bool force_nullable)
    {
        if (function.name == "lambda")
            return;
        FunctionOverloadResolverPtr builder = FunctionFactory::instance().get(function.name, context);
        
        ColumnNumbers dont_visit_children = builder->getArgumentsThatAreAlwaysConstant();
        
        ColumnNumbers can_always_be_nullable = builder->getArgumentsThatDontImplyNullableReturnType(function.arguments->children.size());
        std::vector<char> force_nullable_arguments(function.arguments->children.size(), force_nullable);
        for (auto & idx : can_always_be_nullable)
            if (idx < force_nullable_arguments.size())
                force_nullable_arguments[idx] = true;
        visitChildren(function.arguments, dont_visit_children, force_nullable_arguments);
    }
    bool visitIfLiteral(ASTPtr & ast, bool force_nullable)