[cleanup] Remove unused files (#43188)

dev/integration_tests/android_embedding_2/android/app/build.gradle

-def localProperties = new Properties()
-def localPropertiesFile = rootProject.file('local.properties')
-if (localPropertiesFile.exists()) {
-    localPropertiesFile.withReader('UTF-8') { reader ->
-        localProperties.load(reader)
-    }
-}
-
-def flutterRoot = localProperties.getProperty('flutter.sdk')
-if (flutterRoot == null) {
-    throw new GradleException("Flutter SDK not found. Define location with flutter.sdk in the local.properties file.")
-}
-
-def flutterVersionCode = localProperties.getProperty('flutter.versionCode')
-if (flutterVersionCode == null) {
-    flutterVersionCode = '1'
-}
-
-def flutterVersionName = localProperties.getProperty('flutter.versionName')
-if (flutterVersionName == null) {
-    flutterVersionName = '1.0'
-}
-
-apply plugin: 'com.android.application'
-apply plugin: 'kotlin-android'
-apply from: "$flutterRoot/packages/flutter_tools/gradle/flutter.gradle"
-
-android {
-    compileSdkVersion 28
-
-    sourceSets {
-        main.java.srcDirs += 'src/main/kotlin'
-    }
-
-    lintOptions {
-        disable 'InvalidPackage'
-    }
-
-    defaultConfig {
-        // TODO: Specify your own unique Application ID (https://developer.android.com/studio/build/application-id.html).
-        applicationId "com.example.android_embedding_v2_smoke_test"
-        minSdkVersion 21
-        targetSdkVersion 28
-        versionCode flutterVersionCode.toInteger()
-        versionName flutterVersionName
-        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
-    }
-
-    buildTypes {
-        release {
-            // TODO: Add your own signing config for the release build.
-            // Signing with the debug keys for now, so `flutter run --release` works.
-            signingConfig signingConfigs.debug
-        }
-    }
-}
-
-flutter {
-    source '../..'
-}
-
-dependencies {
-    implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlin_version"
-    testImplementation 'junit:junit:4.12'
-    androidTestImplementation 'androidx.test:runner:1.1.1'
-    androidTestImplementation 'androidx.test.espresso:espresso-core:3.1.1'
-}

dev/integration_tests/android_embedding_2/android/app/src/debug/AndroidManifest.xml

-<manifest xmlns:android="http://schemas.android.com/apk/res/android"
-    package="com.example.android_embedding_v2_smoke_test">
-    <!-- Flutter needs it to communicate with the running application
-         to allow setting breakpoints, to provide hot reload, etc.
-    -->
-    <uses-permission android:name="android.permission.INTERNET"/>
-</manifest>

dev/integration_tests/android_embedding_2/android/app/src/main/kotlin/com/example/android_embedding_2/MainActivity.kt

-package com.example.android_embedding_v2_smoke_test
-
-import androidx.annotation.NonNull;
-import dev.flutter.plugins.GeneratedPluginRegistrant
-import io.flutter.embedding.android.FlutterActivity
-import io.flutter.embedding.engine.FlutterEngine
-
-class MainActivity: FlutterActivity() {
-  override fun configureFlutterEngine(@NonNull flutterEngine: FlutterEngine) {
-    GeneratedPluginRegistrant.registerWith(flutterEngine);
-  }
-}