[Android] Bump Gradle version to 7.6.3 (#5522)

Part of fix for https://github.com/flutter/flutter/issues/138336 by bumping the Gradle version of all package example apps (plus `image_picker_android` plugin) to 7.6.3 from those that had a version below that to fix security vulnerability.

Also fixes a bug I found while using the `update-dependencies` packages tool command that caused it to not catch all of the `gradle-wrapper.properties` files when running with the `gradle` dependency + added a test for the fix.

script/tool/test/update_dependency_command_test.dart

@@ -780,6 +780,73 @@ distributionUrl=https\://services.gradle.org/distributions/gradle-7.6.1-all.zip
                 'gradle-$newGradleVersion-all.zip'));
       });
 
+      test(
+          'succeeds if example app has android/gradle and android/app/gradle directory structure',
+          () async {
+        final RepositoryPackage package =
+            createFakePlugin('fake_plugin', packagesDir, extraFiles: <String>[
+          'example/android/gradle/wrapper/gradle-wrapper.properties',
+          'example/android/app/gradle/wrapper/gradle-wrapper.properties'
+        ]);
+        const String newGradleVersion = '9.9';
+
+        final File gradleWrapperPropertiesFile = package.directory
+            .childDirectory('example')
+            .childDirectory('android')
+            .childDirectory('gradle')
+            .childDirectory('wrapper')
+            .childFile('gradle-wrapper.properties');
+
+        final File gradleAppWrapperPropertiesFile = package.directory
+            .childDirectory('example')
+            .childDirectory('android')
+            .childDirectory('app')
+            .childDirectory('gradle')
+            .childDirectory('wrapper')
+            .childFile('gradle-wrapper.properties');
+
+        gradleWrapperPropertiesFile.writeAsStringSync(r'''
+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-7.6.1-all.zip
+''');
+
+        gradleAppWrapperPropertiesFile.writeAsStringSync(r'''
+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-7.6.1-all.zip
+''');
+
+        await runCapturingPrint(runner, <String>[
+          'update-dependency',
+          '--packages',
+          package.displayName,
+          '--android-dependency',
+          'gradle',
+          '--version',
+          newGradleVersion,
+        ]);
+
+        final String updatedGradleWrapperPropertiesContents =
+            gradleWrapperPropertiesFile.readAsStringSync();
+        final String updatedGradleAppWrapperPropertiesContents =
+            gradleAppWrapperPropertiesFile.readAsStringSync();
+        expect(
+            updatedGradleWrapperPropertiesContents,
+            contains(
+                r'distributionUrl=https\://services.gradle.org/distributions/'
+                'gradle-$newGradleVersion-all.zip'));
+        expect(
+            updatedGradleAppWrapperPropertiesContents,
+            contains(
+                r'distributionUrl=https\://services.gradle.org/distributions/'
+                'gradle-$newGradleVersion-all.zip'));
+      });
+
       test('succeeds if one example app runs on Android and another does not',
           () async {
         final RepositoryPackage package = createFakePlugin(