bind to localhost:0 for tests (#22839)

* bind to localhost:0 for tests

Explicitly bind to `localhost:0` instead of just `:0` to avoid binding to all available interfaces and in turn avoid triggering firewall warnings on MacOS.

* fix Playbooks to use dynamic port

* TestMetrics: handle ipv4 localhost too

* TestMetrics: linting

server/channels/api4/apitestlib.go

@@ -177,7 +177,7 @@ func setupTestHelper(dbStore store.Store, searchEngine *searchengine.Broker, ent
 		*cfg.PasswordSettings.Symbol = false
 		*cfg.PasswordSettings.Number = false
 
-		*cfg.ServiceSettings.ListenAddress = ":0"
+		*cfg.ServiceSettings.ListenAddress = "localhost:0"
 	})
 	if err := th.Server.Start(); err != nil {
 		panic(err)