(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

{
    ExpressionActionsChain::Step & step = chain.lastStep(sourceColumns());
    getRootActions(expr, only_types, step.actions());
    step.addRequiredOutput(expr->getColumnName());
}
ActionsDAGPtr ExpressionAnalyzer::getActionsDAG(bool add_aliases, bool project_result)
{
    auto actions_dag = std::make_shared<ActionsDAG>(aggregated_columns);
    NamesWithAliases result_columns;
    Names result_names;
    ASTs asts;
    if (const auto * node = query->as<ASTExpressionList>())
        asts = node->children;
    else
        asts = ASTs(1, query);
    for (const auto & ast : asts)
    {
        std::string name = ast->getColumnName();
        std::string alias;
        if (add_aliases)
            alias = ast->getAliasOrColumnName();