Cleaning up show status unused fields

[zimulala]

In https://docs.pingcap.com/tidb/stable/sql-statement-show-status#examples the show status results only the following fields:

mysql> SHOW SESSION STATUS;
+-------------------------------+--------------------------------------+
| Variable_name                 | Value                                |
+-------------------------------+--------------------------------------+
| Ssl_cipher                    |                                      |
| Ssl_cipher_list               |                                      |
| Ssl_server_not_after          |                                      |
| Ssl_server_not_before         |                                      |
| Ssl_verify_mode               | 0                                    |
| Ssl_version                   |                                      |
| Uptime                        | 1409                                 |
| ddl_schema_version            | 116                                  |
| last_plan_binding_update_time | 0000-00-00 00:00:00                  |
| server_id                     | 61160e73-ab80-40ff-8f33-27d55d475fd1 |
+-------------------------------+--------------------------------------+

However, when there is a running DDL job, the job information is displayed.

tidb> show status;
+-------------------------------+--------------------------------------+
| Variable_name                 | Value                                |
+-------------------------------+--------------------------------------+
| Ssl_cipher                    |                                      |
| Ssl_cipher_list               |                                      |
| Ssl_server_not_after          |                                      |
| Ssl_server_not_before         |                                      |
| Ssl_verify_mode               | 0                                    |
| Ssl_version                   |                                      |
| Uptime                        | 34                                   |
| ddl_job_action                | create table                         |
| ddl_job_args                  | []                                   |
| ddl_job_error                 |                                      |
| ddl_job_id                    | 109                                  |
| ddl_job_reorg_handle          |                                      |
| ddl_job_row_count             | 0                                    |
| ddl_job_schema_id             | 2                                    |
| ddl_job_schema_state          | none                                 |
| ddl_job_snapshot_ver          | 0                                    |
| ddl_job_start_ts              | 448028215742300161                   |
| ddl_job_state                 | queueing                             |
| ddl_job_table_id              | 108                                  |
| ddl_schema_version            | 52                                   |
| last_plan_binding_update_time | 0000-00-00 00:00:00                  |
| server_id                     | 9cda270d-107f-4ced-a837-edd86583c899 |
+-------------------------------+--------------------------------------+

We will remove DDL job information that is not described in the documentation. Besides, if we want get the DDL job information, we can replace it with admin show ddl;, admin show ddl jobs; or select * from mysql.tidb_ddl_job limit 1;.