(you don't have to strictly follow this form)

**Describe the bug**
When using `ORDER BY column_name COLLATE 'en'`, `COLLATE` is ignored if `column_name` is the primary key
 
**How to reproduce**
* version 21.1.2
* `CREATE TABLE` statements for all tables involved:
```
CREATE TABLE test.test_collation
(
    `v` String,
    `v2` String
)
ENGINE = MergeTree
ORDER BY v
SETTINGS index_granularity = 8192
```
* Sample data:
```
insert into test.test_collation values ('A', 'A')
insert into test.test_collation values ('B', 'B')
insert into test.test_collation values ('C', 'C')
insert into test.test_collation values ('a', 'a')
insert into test.test_collation values ('b', 'b')
insert into test.test_collation values ('c', 'c')
```
* Queries to run that lead to unexpected result
Primary key
```
SELECT *
FROM test.test_collation
ORDER BY v ASC COLLATE 'en'

Query id: fa84ae7a-abe7-4886-99cd-eba7ad5d5fc4

┌─v─┬─v2─┐
│ A │ A  │
│ B │ B  │
│ C │ C  │
│ a │ a  │
│ b │ b  │
│ c │ c  │
└───┴────┘
```
Separate column
```
SELECT *
FROM test.test_collation
ORDER BY v2 ASC COLLATE 'en'

Query id: 04401f85-3cb2-442c-8c89-e3328d1615cd

┌─v─┬─v2─┐
│ a │ a  │
│ A │ A  │
│ b │ b  │
│ B │ B  │
│ c │ c  │
│ C │ C  │
└───┴────┘
```

**Expected behavior**
Both of these queries to return the rows in the same order

NameSet unique_keys;
                ASTs & group_asts = select_query->groupBy()->children;
                for (ssize_t i = 0; i < ssize_t(group_asts.size()); ++i)
                {
                    ssize_t size = group_asts.size();
                    getRootActionsNoMakeSet(group_asts[i], true, temp_actions, false);
                    const auto & column_name = group_asts[i]->getColumnName();
                    const auto * node = temp_actions->tryFindInIndex(column_name);
                    if (!node)
                        throw Exception("Unknown identifier (in GROUP BY): " + column_name, ErrorCodes::UNKNOWN_IDENTIFIER);
                    
                    if (node->column && isColumnConst(*node->column))
                    {
                        
                        if (!aggregate_descriptions.empty() || size > 1)
                        {
                            if (i + 1 < static_cast<ssize_t>(size))
                                group_asts[i] = std::move(group_asts.back());
                            group_asts.pop_back();
                            --i;
                            continue;
                        }
                    }
                    NameAndTypePair key{column_name, node->result_type};
                    
                    if (!unique_keys.count(key.name))
                    {
                        unique_keys.insert(key.name);
                        aggregation_keys.push_back(key);