Handle cases where an add-on is renamed or deleted

[stasadev]

Is there an existing issue for this?

• I have searched the existing issues

Is your feature request related to a problem?

Such situation is not handled.

Describe your solution

Go through all existing files in https://github.com/ddev/addon-registry/tree/main/_addons folder on deploy:

1. Check for removed repos by repo_id, and remove these files.
2. If there are duplicates for repo_id it means that repository was moved, and remove the old file.
3. If repository was renamed, we need to rename existing discussion in https://github.com/ddev/giscus-comments/discussions/categories/add-on-registry-comments to link existing comments to the renamed repo.
   (I'm not sure if we can automate this.)

Describe alternatives

No response

Additional context

No response