chore: add test block that duplicates on drag

[BeksOmega]

The basics

• I validated my changes

The details

Resolves

Fixes N/A

Proposed Changes

Adds a test blocks that duplicates on drag so we can ensure we don't regress in support for that functionality.

Test Coverage

Tested that with my local version of Blockly the block duplicates both when it is a real block and when it is a shadow.

Documentation

N/A

Additional Information

N/A

[cpcallen]

Please fix lint warnings.

Is there (or will there be) a corresponding Blockly to add a test that exercises this functionality? If so, please add a comment to this PR referencing it.

[BeksOmega]

I'm not going to fix the lint warnings. imo the code is readable and sufficient for testing. I think for test code it's allowable to ignore the warning - that's why it's not an error.

ATM there's not going to be a test in core exercising this - it will just need to be manually tested. It might be possible to test this with a webdriver test? but dealing with the circular dependencies to get that working is not a high priority for me right now.