feat!: remove a relay immediately instead of unpublishing it

Removing a relay now takes effect immediately:

- the profile stops fetching and advertising it,

- secondary devices immediately apply the removal through the transport sync,

Upgrading removes unpublished relays and triggers keyupdates.

BREAKING CHANGE: set_transport_unpublished() is removed: UIs call delete_transport() when the user removes a relay.

BREAKING CHANGE: list_transports_ex() and the TransportListEntry type are removed: use list_transports().

BREAKING CHANGE: delete_transport() no longer refuses to remove the primary transport: it refuses only to remove the last one and re-elects the sending transport as needed.

BREAKING CHANGE: TransportsModified is now also emitted on the device modifying the transports, not only on devices applying the synced change.

Deprecated: DC_STR_PHASING_OUT

src/test_utils.rs

@@ -567,7 +567,7 @@ impl TestContext {
         }
     }
 
-    /// Adds a published transport for `addr` without any network activity.
+    /// Adds a transport for `addr` without any network activity.
     pub async fn add_transport(&self, addr: &str) {
         add_pseudo_transport(self, addr).await.unwrap();
         // A fresh `add_timestamp` makes the re-signed self key newer than the copies