please add a param to control the number of lines which displayed in "show import jobs result"

## Feature Request

**Is your feature request related to a problem? Please describe:**
currently, "show import jobs" command will return all the lines in jobs,
maybe we need add a param to control the displayed rows of this command, in case the result is too much.
we can add a param like "show ddl jobs", the default display lines are 20, and you can add a expect number as command "show ddl jobs 5"
and maybe we can support use "show import jobs" with "where " condition.

**Describe the feature you'd like:**

**Describe alternatives you've considered:**

**Teachability, Documentation, Adoption, Migration Strategy:**