Fix duplicate labels when moving projects

What does this MR do?

When a project is moved to a different group, we create labels that don't exist in the new group so that issues and MRs would have the same labels.

But there is a bug where we didn't account for ancestor group labels. When a project is moved within the same ancestor group, we still created ancestor group labels even if they are still available in the new group. This MR fixes this problem.

Related to #22141 (closed)

Screenshots

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team