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/app/helper_test.go

@@ -102,7 +102,7 @@ func setupTestHelper(dbStore store.Store, enterprise bool, includeCacheLayer boo
 	th.App.UpdateConfig(func(cfg *model.Config) { *cfg.TeamSettings.MaxUsersPerTeam = 50 })
 	th.App.UpdateConfig(func(cfg *model.Config) { *cfg.RateLimitSettings.Enable = false })
 	prevListenAddress := *th.App.Config().ServiceSettings.ListenAddress
-	th.App.UpdateConfig(func(cfg *model.Config) { *cfg.ServiceSettings.ListenAddress = ":0" })
+	th.App.UpdateConfig(func(cfg *model.Config) { *cfg.ServiceSettings.ListenAddress = "localhost:0" })
 	serverErr := th.Server.Start()
 	if serverErr != nil {
 		panic(serverErr)