Remove nest event media files that are no longer referenced

[allenporter]

Proposed change

Remove nest event media files that are no longer referenced in the event database. This will ensure no stale media files are being left around and being persisted, which may be bloating users backups.

There appears to be cases where existing garbage collection not always removing things. This cleanup is needed even after that is fixed.

Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
• New integration (thank you!)
• New feature (which adds functionality to an existing integration)
• Deprecation (breaking change to happen in the future)
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code or addition of tests

Additional information

• This PR fixes or closes issue:
• This PR is related to issue: Nest integration bloats HA backups #122434
• Link to documentation pull request:
• Link to developer documentation pull request:
• Link to frontend pull request:

Checklist

• The code change is tested and works locally.
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• The code has been formatted using Ruff (ruff format homeassistant tests)
• Tests have been added to verify that the new code works.

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• Documentation added/updated for www.home-assistant.io

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