Add support for remote-specific S3 object deletion using hierarchical key prefixes.
When a remote parameter is provided, only objects under that remote's hierarchy
(e.g., 'fedora/*') are deleted, preserving cached files for other remotes.
Key improvements:
- Use S3 list_objects_v2 Prefix parameter for targeted deletion
- Enhanced logging to indicate scope of cache clearing operations
- Backward compatible - existing behavior preserved when no remote specified
Resolves artifactapi-u46
