…ling entirely if one fetch fails

- Fix documentation
- Add `--registry` flag to support multi-registry open beta endpoints

…to docr/multi-registry

- Fixed command structure mismatches between legacy registry and new registries commands
- Updated API endpoints from /v2/registry/ to /v2/registries/ where needed
- Corrected parameter order (added registry-name as first parameter for registries commands)
- Fixed expected output messages to match actual command responses
- Added support for both legacy and multi-registry endpoints in test servers

Tests fixed:
- registry_delete_tag_test.go
- registries_list_repositories_test.go
- registries_options_test.go
- registry_delete_manifest_test.go
- registries_list_repository_tags_test.go
- registry_garbagecollection_test.go