Add structured logging to all importers
<!--IssueSummary start--> <details> <summary> Everyone can contribute. [Help move this issue forward](https://handbook.gitlab.com/handbook/marketing/developer-relations/contributor-success/community-contributors-workflows/#contributor-links) while earning points, leveling up and collecting rewards. </summary> - [Close this issue](https://contributors.gitlab.com/manage-issue?action=close&projectId=278964&issueIid=25870) </details> <!--IssueSummary end--> We should use the new import logger: `Gitlab::Import::Logger.build` We have some importers with such logging enabled, but we should enable this probably at `import_service.rb` level and pass it to each importer #### Technical Note: The labkit-ruby upgrade (part of upgrading to Ruby 3.0) injects info into logs - to track which deployment stage we execute on (main, cny)- _after_ the event leaves gitlab-rails. Since it writes the `stage` log field, it overwrites any `stage:` value, so don't use this value in the logs. See !111590
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