Map labels from Jira to labels in GitLab

What does this MR do?

It moves labels imported for issues from the Jira from GitLab issue description (metadata section) to label field.

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.

Issue: #212948 (closed)