add wait handlers for custom domains and distributions

[malteehrlen]

Description

Add wait handlers for CDN resources https://jira.schwarz/browse/STACKITCDN-716

I just saw that a wait handler was already added, please consider this contribution as extending the existing handler with handlers also for custom domains

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)
• 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)