Keep the declarations retired once their stream is gone, so nothing expects, asserts or makes NODES again (issue 1945)

A node-engine newer than the registered one, or a node asleep on an older
have, made the done test false after the start deleted NODES; the bus's
health check, probes D6 and D7 and healer H3 then expected the stream and
every node's consumer again, raised them urgent and made them anew. Release
6 sends no declaration, so a stream made again helps no node: a gone stream
is retired. The advisory watchdog also reads a consumer whose stream is gone
as gone instead of failing.

cmd/mesh-controller/composed_integration_test.go

@@ -140,4 +140,35 @@ func TestTheDeclarationsStreamGoesOnceEveryNodeRunsTheNewEngine(t *testing.T) {
 	if !declarationsRetiredNow(ctx, m.open.inventory) {
 		t.Errorf("a raise after the retirement would assert the stream again")
 	}
+
+	// Issue 1945: a node-engine other than the registered one landing on laptop (a newer build on its way) leaves the
+	// declarations retired, so what the health check, the probes and healer H3 expect of the bus names neither the
+	// stream nor a node's consumer on it, and asserting the bus's objects again does not make the stream anew.
+	have("laptop", fpOf('7'))
+	if !declarationsRetiredNow(ctx, m.open.inventory) {
+		t.Fatalf("with laptop on another node-engine after the stream went, the declarations are no longer retired")
+	}
+	streams, consumers, err := expectedBusObjects(ctx, m.open.inventory)
+	if err != nil {
+		t.Fatal(err)
+	}
+	for _, s := range streams {
+		if s.Name == broker.DeclarationsStream {
+			t.Errorf("the bus's health check and probe D7 still expect the stream %s", s.Name)
+		}
+	}
+	for _, c := range consumers {
+		if c.Stream == broker.DeclarationsStream {
+			t.Errorf("the bus's health check and probe D6 still expect %s on %s", c.Name, c.Stream)
+		}
+	}
+	bus, err := broker.Dial(m.conn.ConnectedUrl())
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(bus.Close)
+	_ = assertOnSend(ctx, m.open.inventory, bus, "  ")
+	if _, err := m.js.Stream(ctx, broker.DeclarationsStream); !errors.Is(err, jetstream.ErrStreamNotFound) {
+		t.Errorf("healer H3's assertion of the bus's objects made the stream anew: %v", err)
+	}
 }