feat(cdn) refactor waiters to use WaiterHelper

[cgoetz-inovex]

Description

relates to #1234

Checklist

• Issue was linked above
• No generated code was adjusted manually (check comments in file header)
• Changelogs
  • Changelog in the root directory was adjusted (see here)
  • Changelog(s) of the service(s) were adjusted (see e.g. here)
• VERSION file(s) of the service(s) were adjusted
• Code format was applied: make fmt
• Examples were added / adjusted (see examples/ directory)
• Unit tests got implemented or updated
• Unit tests are passing: make test (will be checked by CI)
• No linter issues: make lint (will be checked by CI)

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[github-actions]

This PR was marked as stale after 7 days of inactivity and will be closed after another 7 days of further inactivity. If this PR should be kept open, just add a comment, remove the stale label or push new commits to it.

[github-actions]

This PR was closed automatically because it has been stalled for 7 days with no activity. Feel free to re-open it at any time.