plugin: Add featurebits registered by plugins to node_announcements

This is the last venue we need to add custom featurebits to, so we also unmark
the test as xfail.

Changelog-Added: plugin: Plugins can now signal support for experimental protocol extensions by registering featurebits for `node_announcement`s, the connection handshake, and for invoices. For now this is limited to non-dynamic plugins only

lightningd/gossip_control.c

@@ -191,7 +191,7 @@ static void gossip_topology_synced(struct chain_topology *topo, void *unused)
  * message */
 void gossip_init(struct lightningd *ld, int connectd_fd)
 {
-	u8 *msg;
+	u8 *msg, *node_featurebits;
 	int hsmfd;
 
 	hsmfd = hsm_get_global_fd(ld, HSM_CAP_SIGN_GOSSIP);
@@ -206,11 +206,16 @@ void gossip_init(struct lightningd *ld, int connectd_fd)
 	topology_add_sync_waiter(ld->gossip, ld->topology,
 				 gossip_topology_synced, NULL);
 
+	node_featurebits =
+	    featurebits_or(tmpctx, take(get_offered_nodefeatures(tmpctx)),
+			   take(plugins_collect_featurebits(
+			       tmpctx, ld->plugins, PLUGIN_FEATURES_NODE)));
+
 	msg = towire_gossipctl_init(
 	    tmpctx,
 	    chainparams,
 	    &ld->id,
-	    get_offered_nodefeatures(tmpctx),
+	    node_featurebits,
 	    ld->rgb,
 	    ld->alias,
 	    ld->announcable,

tests/test_plugin.py

@@ -826,7 +826,6 @@ def test_libplugin(node_factory):
     assert l1.rpc.call("testrpc") == l1.rpc.getinfo()
 
 
-@pytest.mark.xfail(strict=True)
 @unittest.skipIf(not DEVELOPER, "needs LIGHTNINGD_DEV_LOG_IO")
 def test_plugin_feature_announce(node_factory):
     """Check that features registered by plugins show up in messages.