[IJ Plugin] v3 -> v4 Migration: add @link imports for used kotlin_labs directives

[BoD]

Currently, kotlin_labs definitions are imported implicitly, so they don't need to be imported, but we probably intend to change this in the future, making the explicit @link import necessary.

In #5413 we already show a warning for such missing imports.

The migration helper could automatically add the imports, to avoid warnings and ease of transition to the future behavior change.

[BoD]

Fix is released in 4.0.0-beta.7

[github-actions]

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