Add a second variant of ReadOnlyNetworkGraph::get_addresses for C

We cannot expose ReadOnlyNetworkGraph::get_addresses in C as it
returns a list of references to an enum, which the bindings dont
support. Instead, we add a second `#[doc(hidden)]` variant which
the C bindings will expose (and document).

Author: TheBlueMatt

lightning/src/routing/network_graph.rs

@@ -1223,6 +1223,19 @@ impl ReadOnlyNetworkGraph<'_> {
 		}
 		None
 	}
+
+	#[doc(hidden)] // Note that this will be ignored in C bindings generation
+	/// Get network addresses by node id.
+	/// Returns None if the requested node is completely unknown,
+	/// or if node announcement for the node was never received.
+	pub fn get_node_addresses(&self, pubkey: &PublicKey) -> Option<Vec<NetAddress>> {
+		if let Some(node) = self.nodes.get(pubkey) {
+			if let Some(node_info) = node.announcement_info.as_ref() {
+				return Some(node_info.addresses.clone())
+			}
+		}
+		None
+	}
 }
 
 #[cfg(test)]