Column alias might fail in the ORDER BY's subquery clause.

## Bug Report

Please answer these questions before submitting your issue. Thanks!

### 1. Minimal reproduce step (Required)

```
DROP TABLE IF EXISTS t1, t2;
CREATE TABLE t1 (a INT, b INT);
CREATE TABLE t2 (a INT, b INT);
INSERT INTO t1 VALUES (1, 1);
INSERT INTO t2 VALUES (1, 1);

SELECT one.a, one.b as b2 FROM t1 one ORDER BY (SELECT two.b FROM t2 two WHERE two.a = b2);
```

### 2. What did you expect to see? (Required)

The query was executed successfully.

### 3. What did you see instead (Required)

Error reported that column `b2` in the ORDER BY clause is not found.

### 4. What is your TiDB version? (Required)

current master