The binary etc were renamed some time ago, but the path in the source
tree remained "attachment_service" to avoid disruption to ongoing PRs.
There aren't any big PRs out right now, so it's a good time to cut over.
- Rename `attachment_service` to `storage_controller`
- Move it to the top level for symmetry with `storage_broker` & to avoid
mixing the non-prod neon_local stuff (`control_plane/`) with the storage
controller which is a production component.
## Problem
During incidents, we may need to quickly access the storage controller's
API without trying API client code or crafting `curl` CLIs on the fly. A
basic CLI client is needed for this.
## Summary of changes
- Update storage controller node listing API to only use public types in
controller_api.rs
- Add a storage controller API for listing tenants
- Add a basic test that the CLI can list and modify nodes and tenants.
