MM-13606 Remove consumeAndClose and clean up integration response handling (#10066)

* MM-13606 Remove consumeAndClose

* Allow overriding HTTPService's request timeout

* MM-13606 Clean up integration response handling

* Properly close httptest servers

* Address feedback

* Only call buf.Bytes when necessary

* Properly check for errors in doOutgoingWebhookRequest

* Add comment explaining ignored ioutil.ReadAll errors

services/httpservice/client.go

@@ -126,10 +126,3 @@ func NewTransport(enableInsecureConnections bool, allowHost func(host string) bo
 		},
 	}
 }
-
-func NewHTTPClient(transport http.RoundTripper) *http.Client {
-	return &http.Client{
-		Transport: transport,
-		Timeout:   RequestTimeout,
-	}
-}