Should return warning instead of error for truncated argument in `sec_to_time`.

## Bug Report

Please answer these questions before submitting your issue. Thanks!

### 1. Minimal reproduce step (Required)

Run `SELECT sec_to_time(3020399.999999)`.

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

```
mysql> SELECT sec_to_time(3020399.999999);
+-----------------------------+
| sec_to_time(3020399.999999) |
+-----------------------------+
| 838:59:59.000000 |
+-----------------------------+
1 row in set, 1 warning (0.01 sec)

mysql> show warnings;
+---------+------+--------------------------------------------------+
| Level | Code | Message |
+---------+------+--------------------------------------------------+
| Warning | 1292 | Truncated incorrect time value: '3020399.999999' |
+---------+------+--------------------------------------------------+
1 row in set (0.00 sec)
```

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

```
mysql> SELECT sec_to_time(3020399.999999);
ERROR 1292 (22007): Truncated incorrect time value: '838:59:59.999999000225216'
```

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