(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

const ManyExpressionActions & elements_actions_,
    const SortDescription & required_sort_description_,
    const TreeRewriterResultPtr & syntax_result)
    : elements_actions(elements_actions_)
    , required_sort_description(required_sort_description_)
{
    if (elements_actions.size() != required_sort_description.size())
        throw Exception("Sizes of sort description and actions are mismatched", ErrorCodes::LOGICAL_ERROR);
    
    
    
    forbidden_columns = syntax_result->getArrayJoinSourceNameSet();
}
InputOrderInfoPtr ReadInOrderOptimizer::getInputOrder(const StorageMetadataPtr & metadata_snapshot, ContextPtr context) const
{
    Names sorting_key_columns = metadata_snapshot->getSortingKeyColumns();
    if (!metadata_snapshot->hasSortingKey())
        return {};
    SortDescription order_key_prefix_descr;
    int read_direction = required_sort_description.at(0).direction;
    size_t prefix_size = std::min(required_sort_description.size(), sorting_key_columns.size());
    auto aliase_columns = metadata_snapshot->getColumns().getAliases();