The character set of the result of `NOT` is binary, which is different from MySQL

## Bug Report

Please answer these questions before submitting your issue. Thanks!

### 1. Minimal reproduce step (Required)

```
CREATE TABLE t1 (a INT, b VARCHAR(10)); INSERT INTO t1 VALUES (0, '0'); SELECT NOT a COLLATE utf8mb4_bin = b FROM t1;
```

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

```
mysql> CREATE TABLE t1 (a INT, b VARCHAR(10)); INSERT INTO t1 VALUES (0, '0'); SELECT NOT a COLLATE utf8mb4_bin = b FROM t1;
Query OK, 0 rows affected (0.07 sec)

Query OK, 1 row affected (0.01 sec)

+-------------------------------+
| NOT a COLLATE utf8mb4_bin = b |
+-------------------------------+
| 0 |
+-------------------------------+
1 row in set (0.00 sec)
```

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

```
mysql> CREATE TABLE t1 (a INT, b VARCHAR(10)); INSERT INTO t1 VALUES (0, '0'); SELECT NOT a COLLATE utf8mb4_bin = b FROM t1;
Query OK, 0 rows affected (0.05 sec)

Query OK, 1 row affected (0.01 sec)

ERROR 1253 (42000): COLLATION 'utf8mb4_bin' is not valid for CHARACTER SET 'binary'
```

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