Migrate integration_test plugin to Gradle Kotlin DSL (#142008)

We already have a simple app in this repo that fully uses Gradle Kotlin DSL (see #141541). The next small step is to have at least one plugin that also uses Gradle Kotlin DSL. Let's use `integration_test` for that, since it's versioned with Flutter SDK.

packages/integration_test/android/build.gradle

@@ -1,64 +0,0 @@
-// Copyright 2014 The Flutter Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-group 'dev.flutter.plugins.integration_test'
-version '1.0-SNAPSHOT'
-
-buildscript {
-    repositories {
-        google()
-        mavenCentral()
-    }
-
-    dependencies {
-        classpath 'com.android.tools.build:gradle:7.3.1'
-    }
-}
-
-rootProject.allprojects {
-    repositories {
-        google()
-        mavenCentral()
-    }
-}
-
-// project.getTasks().withType(JavaCompile){
-//     options.compilerArgs << "-Xlint:all" << "-Werror"
-// }
-
-apply plugin: 'com.android.library'
-
-android {
-    // Conditional for compatibility with AGP <4.2.
-    if (project.android.hasProperty("namespace")) {
-        namespace 'dev.flutter.integration_test'
-    }
-
-    compileSdk 34
-
-    compileOptions {
-        sourceCompatibility JavaVersion.VERSION_1_8
-        targetCompatibility JavaVersion.VERSION_1_8
-    }
-
-    defaultConfig {
-        minSdkVersion 21
-        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
-        consumerProguardFiles 'lib-proguard-rules.txt'
-    }
-
-    dependencies {
-        // TODO(egarciad): These dependencies should not be added to release builds.
-        // https://github.com/flutter/flutter/issues/56591
-        testImplementation 'junit:junit:4.12'
-        testImplementation 'org.mockito:mockito-inline:5.0.0'
-
-        // https://developer.android.com/jetpack/androidx/releases/test/#1.2.0
-        api 'androidx.test:runner:1.2.0'
-        api 'androidx.test:rules:1.2.0'
-        api 'androidx.test.espresso:espresso-core:3.2.0'
-
-        implementation 'com.google.guava:guava:28.1-android'
-    }
-}

packages/integration_test/android/build.gradle.kts

@@ -0,0 +1,63 @@
+// Copyright 2014 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+group = "dev.flutter.plugins.integration_test"
+version = "1.0-SNAPSHOT"
+
+buildscript {
+    repositories {
+        google()
+        mavenCentral()
+    }
+
+    dependencies {
+        classpath("com.android.tools.build:gradle:7.3.1")
+    }
+}
+
+plugins {
+    id("com.android.library")
+}
+
+rootProject.allprojects {
+    repositories {
+        google()
+        mavenCentral()
+    }
+}
+
+android {
+    // Conditional for compatibility with AGP <4.2.
+    if (project.findProject("android")?.hasProperty("namespace") == true) {
+        namespace = "dev.flutter.integration_test"
+    }
+
+    namespace = "dev.flutter.integration_test"
+    compileSdk = 34
+
+    compileOptions {
+        sourceCompatibility = JavaVersion.VERSION_1_8
+        targetCompatibility = JavaVersion.VERSION_1_8
+    }
+
+    defaultConfig {
+        minSdk = 21
+        testInstrumentationRunner = "androidx.test.runner.AndroidJUnitRunner"
+        consumerProguardFiles("lib-proguard-rules.txt")
+    }
+
+    dependencies {
+        // TODO(egarciad): These dependencies should not be added to release builds.
+        // https://github.com/flutter/flutter/issues/56591
+        testImplementation("junit:junit:4.12")
+        testImplementation("org.mockito:mockito-inline:5.0.0")
+
+        // https://developer.android.com/jetpack/androidx/releases/test/#1.2.0
+        api("androidx.test:runner:1.2.0")
+        api("androidx.test:rules:1.2.0")
+        api("androidx.test.espresso:espresso-core:3.2.0")
+
+        implementation("com.google.guava:guava:28.1-android")
+    }
+}

packages/integration_test/android/settings.gradle.kts

@@ -2,4 +2,4 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-rootProject.name = 'integrationTest'
+rootProject.name = "integrationTest"