Store labels from jira issues as labels on gitlab issues

In #209792 (closed) we simply added the labels assigned to issues on Jira to metadata section in GitLab issue description.

We should, however, create labels for GitLab issues appropriately.

In case a label exists on the project, we should use that label. In case the label does not exist we should create a new one.

From #212651 (closed):

Jira REST API has a dedicated endpoint to pull all the labels in a project https://developer.atlassian.com/cloud/jira/platform/rest/v2/#api-rest-api-2-label-get we can use that to import all labels in batches, cache them and link the issues to the specific label. We have a dedicated stage for that as well Gitlab::JiraImport::ImportLabelsWorker app/workers/gitlab/jira_import/stage/import_labels_worker.rb