`CONVERT_TZ` is not compatible with MySQL for edging value

## Bug Report

Please answer these questions before submitting your issue. Thanks!

### 1. Minimal reproduce step (Required)

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

```
mysql> SELECT CONVERT_TZ('0000-01-01 00:00:00', '+00:00', '+01:00');
+-------------------------------------------------------+
| CONVERT_TZ('0000-01-01 00:00:00', '+00:00', '+01:00') |
+-------------------------------------------------------+
| 0000-01-01 00:00:00 |
+-------------------------------------------------------+
1 row in set (0.01 sec)

mysql> SELECT CONVERT_TZ('9999-12-31 23:59:59', 'UTC', 'Asia/Kolkata');
+----------------------------------------------------------+
| CONVERT_TZ('9999-12-31 23:59:59', 'UTC', 'Asia/Kolkata') |
+----------------------------------------------------------+
| 9999-12-31 23:59:59 |
+----------------------------------------------------------+
1 row in set (0.00 sec)

```

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

```

mysql> SELECT CONVERT_TZ('0000-01-01 00:00:00', '+00:00', '+01:00');
+-------------------------------------------------------+
| CONVERT_TZ('0000-01-01 00:00:00', '+00:00', '+01:00') |
+-------------------------------------------------------+
| 0000-01-01 01:00:00 |
+-------------------------------------------------------+
1 row in set (0.00 sec)

mysql> SELECT CONVERT_TZ('9999-12-31 23:59:59', 'UTC', 'Asia/Kolkata');
+----------------------------------------------------------+
| CONVERT_TZ('9999-12-31 23:59:59', 'UTC', 'Asia/Kolkata') |
+----------------------------------------------------------+
| 10000-01-01 05:29:59 |
+----------------------------------------------------------+
1 row in set (0.00 sec)
```

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

Start by reproducing the two CONVERT_TZ queries from the issue and comparing TiDB's results with MySQL. No implementation file or test is named, so trace the CONVERT_TZ entry point and existing date/time tests; done means both edge cases match the expected MySQL results.

Written by the indexing model from the issue text.