[webview_flutter] Fix macOS 14+ test hangs (#7953)

Starting in macOS 14, webview_flutter integration tests hang due to being unable to connect to the test server. Based on local experimentation, in appears that we are not able to connect when binding to the "any" address, which gives us an IP address of 0.0.0.0, but using the loopback address (which is all we should need; the point is to accept local connections from the test itself) does work.

Since our test fleet is a mixed macOS 13/14 fleet, this should fix flaky timeouts of macOS platform tests in CI, in addition to fixing local runs.

Fixes flutter/flutter#157449

packages/webview_flutter/webview_flutter/example/integration_test/webview_flutter_test.dart

@@ -22,7 +22,8 @@ import 'package:webview_flutter_wkwebview/webview_flutter_wkwebview.dart';
 Future<void> main() async {
   IntegrationTestWidgetsFlutterBinding.ensureInitialized();
 
-  final HttpServer server = await HttpServer.bind(InternetAddress.anyIPv4, 0);
+  final HttpServer server =
+      await HttpServer.bind(InternetAddress.loopbackIPv4, 0);
   unawaited(server.forEach((HttpRequest request) {
     if (request.uri.path == '/hello.txt') {
       request.response.writeln('Hello, world.');

packages/webview_flutter/webview_flutter/example/integration_test/webview_flutter_test_legacy.dart

@@ -20,7 +20,8 @@ import 'package:webview_flutter/src/webview_flutter_legacy.dart';
 Future<void> main() async {
   IntegrationTestWidgetsFlutterBinding.ensureInitialized();
 
-  final HttpServer server = await HttpServer.bind(InternetAddress.anyIPv4, 0);
+  final HttpServer server =
+      await HttpServer.bind(InternetAddress.loopbackIPv4, 0);
   unawaited(server.forEach((HttpRequest request) {
     if (request.uri.path == '/hello.txt') {
       request.response.writeln('Hello, world.');

packages/webview_flutter/webview_flutter_wkwebview/example/integration_test/legacy/webview_flutter_test.dart

@@ -29,7 +29,8 @@ const bool skipOnIosFor154676 = true;
 Future<void> main() async {
   IntegrationTestWidgetsFlutterBinding.ensureInitialized();
 
-  final HttpServer server = await HttpServer.bind(InternetAddress.anyIPv4, 0);
+  final HttpServer server =
+      await HttpServer.bind(InternetAddress.loopbackIPv4, 0);
   unawaited(server.forEach((HttpRequest request) {
     if (request.uri.path == '/hello.txt') {
       request.response.writeln('Hello, world.');

packages/webview_flutter/webview_flutter_wkwebview/example/integration_test/webview_flutter_test.dart

@@ -24,7 +24,8 @@ import 'package:webview_flutter_wkwebview/webview_flutter_wkwebview.dart';
 Future<void> main() async {
   IntegrationTestWidgetsFlutterBinding.ensureInitialized();
 
-  final HttpServer server = await HttpServer.bind(InternetAddress.anyIPv4, 0);
+  final HttpServer server =
+      await HttpServer.bind(InternetAddress.loopbackIPv4, 0);
   unawaited(server.forEach((HttpRequest request) {
     if (request.uri.path == '/hello.txt') {
       request.response.writeln('Hello, world.');