Clean up Unused Secrets

[wangeguo]

When amp-configurations is modified, Configuration Watcher listens for changes and usually updates the corresponding Secret and Service Account. There are three possible scenarios:

1. If there are no new modifications, there are no substantial changes (Kubernetes will not perform any update operations if no changes are detected).
   2 If any new registry or repository is added during the modification, Configuration Watcher synchronizes the creation of corresponding registry secrets or repo secrets.
2. If any registry or repository is no longer used, its corresponding Secret must be deleted. Unfortunately, this scenario is not yet supported.

To fix this issue, we propose comparing the current amp-configurations with the new amp-configuration and creating Secrets for new items while deleting the Secrets for any missing items.

See: https://github.com/amphitheatre-app/amphitheatre/blob/master/resources/src/credential.rs#L39