Change default seeding scope to 'all' — heartwood

This makes the default policy block with scope all. The good thing about this is that you don’t have to manage individual nodes in the beginning. You simply seed the repos you want, and everything is followed within those repos. This matches user expectations, as rad seed does what you expect it to do.

For open-policy seed nodes, it also means that simply changing block to allow from the default config is all you need.

This leaves the non-default followed scope as a more “advanced” setting, since it is much more cumbersome: it forces you to follow a user before you can see their issues/patches, which is not something most users expect coming from old-shcool forges.

 have its policy set to allow seeding:
 ```
 $ rad inspect rad:z42hL2jL4XNk6K8oHQaSWfMgCL7ji --policy
 Repository rad:z42hL2jL4XNk6K8oHQaSWfMgCL7ji is being seeded with scope `followed`
 Repository rad:z42hL2jL4XNk6K8oHQaSWfMgCL7ji is being seeded with scope `all`
 ```
 Since there is no policy specific to this repository, there's nothing to be

       }
     },
     "policy": "block",
     "scope": "followed"
     "scope": "all"
   }
 }
 ```

                     }
                   },
                   "policy": "block",
                   "scope": "followed"
                   "scope": "all"
                 }
               },
               "home": seed.profile.path()

 #[serde(rename_all = "camelCase")]
 pub enum Scope {
     /// Seed remotes that are explicitly followed.
     #[default]
     Followed,
     /// Seed all remotes.
     #[default]
     All,
 }