CleanupMockitoImports should not remove used mockito kotlin imports

[gideon-sunbit]

What's changed?

Add a NoMissingTypes Precondition to CleanupMockitoImports, to prevent changes if types are missing

What's your motivation?

Fix issue where org.mockito.kotlin imports were being removed although they were in use.
Following suggestion by @timtebeek in Slack channel.

Anything in particular you'd like reviewers to focus on?

Possibly the unit test should use a Kotlin code block and not a Java one? not sure about this.

Anyone you would like to review specifically?

@timtebeek

Checklist

• I've added unit tests to cover both positive and negative cases
• I've read and applied the recipe conventions and best practices
• I've used the IntelliJ IDEA auto-formatter on affected files

[timtebeek]

Thanks for getting this started! Didn't realize in Slack that it was Mockito Kotlin imports that were incorrectly removed. With that knowledge I've now added special handling, as we kind of expect missing types when it comes to converting Mockito test classes. Hope this works for your real use case too; do let me know when you try our snapshot versions.