Make generate_gradle_lockfiles also write the gradle wrapper file (#142329)

The `generate_gradle_lockfiles` script currently writes the top level `build.gradle` file and the `settings.gradle` file, and is the easiest way to batch update these files to, for example, increase the AGP version used in integration tests and examples across the framework repo.

This PR makes it also write the gradle version, so that we can do batch upgrades of our gradle version with it as well.

dev/tools/bin/generate_gradle_lockfiles.dart

@@ -40,6 +40,15 @@ void main(List<String> arguments) {
       continue;
     }
 
+    final File wrapperGradle = androidDirectory
+        .childDirectory('gradle')
+        .childDirectory('wrapper')
+        .childFile('gradle-wrapper.properties');
+    if (!wrapperGradle.existsSync()) {
+      print('${wrapperGradle.path} does not exist - skipping');
+      continue;
+    }
+
     if (settingsGradle.readAsStringSync().contains('include_flutter.groovy')) {
       print('${settingsGradle.path} add to app - skipping');
       continue;
@@ -78,6 +87,7 @@ void main(List<String> arguments) {
 
     rootBuildGradle.writeAsStringSync(rootGradleFileContent);
     settingsGradle.writeAsStringSync(settingGradleFile);
+    wrapperGradle.writeAsStringSync(wrapperGradleFileContent);
 
     final String appDirectory = androidDirectory.parent.absolute.path;
 
@@ -214,3 +224,11 @@ include ":app"
 
 apply from: "${settings.ext.flutterSdkPath}/packages/flutter_tools/gradle/app_plugin_loader.gradle"
 ''';
+
+const String wrapperGradleFileContent = r'''
+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-7.6.3-all.zip
+''';