Check disallowed imports in agent instrumentation classes

[kezhenxu94]

Please answer these questions before submitting pull request

• Why submit this pull request?

• Bug fix

• New feature provided

• Improve performance

• Enhancement

• Related issues

As described in #2871 , we merged a PR that breaks the agent by importing external classes, and a script to check that is provided in #2881 , here I'm proposing another way to check this before our contributors commit and push their codes, by leveraging the checkstyle plugin, if the contributors have a checkstyle plugin installed in their IDE, it would show an error when writing codes, before submitting, which would save some time.

[wu-sheng]

Check style module is being removed, right?
And do I still need that scripts to check? Could we remove that?

[kezhenxu94]

Check style module is being removed, right?

Yes, the module is just used for holding the checkstyle.xml file, and the file can be simply placed in the directory. After removing it, changing the checkstyle.xml doesn't require a deployment of that module.

And do I still need that scripts to check? Could we remove that?

Removing it or not is both ok to me as long as it does no harm

[wu-sheng]

If you can remove, remove. Because we need consistent configuration in one place. With this PR, it shows in both places.

[kezhenxu94]

If you can remove, remove. Because we need consistent configuration in one place. With this PR, it shows in both places.

done

[dmsolr]

You are so fast @kezhenxu94 . I'm going to do it.

[wu-sheng]

LGTM. Thank you and @dmsolr to make this feature better.