feat(registry): import-command: remove dangling manifest option
Related to: Exploring the possible failure modes for in pla... (#901 - closed)
This MR removes the dangling manifest option from the user-facing command. Dangling manifests are not preserved by garbage collection, and their import is not included in the design for the self-managed import.
We're not able to fully remove this feature yet, as many importer integration tests require it.