refactor: move httptransport w/ logging to netxlite (#411)

Part of https://github.com/ooni/probe/issues/1505

internal/netxmocks/http_test.go

@@ -0,0 +1,38 @@
+package netxmocks
+
+import (
+	"errors"
+	"net/http"
+	"testing"
+
+	"github.com/ooni/probe-cli/v3/internal/atomicx"
+)
+
+func TestHTTPTransportRoundTrip(t *testing.T) {
+	expected := errors.New("mocked error")
+	txp := &HTTPTransport{
+		MockRoundTrip: func(req *http.Request) (*http.Response, error) {
+			return nil, expected
+		},
+	}
+	resp, err := txp.RoundTrip(&http.Request{})
+	if !errors.Is(err, expected) {
+		t.Fatal("not the error we expected", err)
+	}
+	if resp != nil {
+		t.Fatal("expected nil response here")
+	}
+}
+
+func TestHTTPTransportCloseIdleConnections(t *testing.T) {
+	called := &atomicx.Int64{}
+	txp := &HTTPTransport{
+		MockCloseIdleConnections: func() {
+			called.Add(1)
+		},
+	}
+	txp.CloseIdleConnections()
+	if called.Load() != 1 {
+		t.Fatal("not called")
+	}
+}