Stacked patch on https://app.radicle.xyz/nodes/seed.radicle.xyz/rad:z3gqcJUoA1n9HaHKufZs5FCSGazv5/patches/bd89ef967eb6b53784b8913280a7a4da27c25ac8

Base: 4de47ffff4277e42a211b8b7214161cafd830b84

radicle: return iterator types for db policies

Instead of collecting the results and returning the collection as an iterator, introduce FollowPolicies and SeedPolicies types, which implement Iterator.

Note that a call in service changed due to the lifetime borrow. It simply collects into a Vec for the time being.

Rebased