[Improve] add filter condition for some manager command

In practice, the result of following manager commands is too long. It's difficult for user to find valid information. So, we provide where condition to filter.

show @@connection, support following condition:

- PROCESSOR
- FRONT_ID
- HOST
- USER

show @@backend, support following condition:

- PROCESSOR
- BACKEND_ID
- MYSQL_ID
- HOST
- PORT