Migrate play-services and example-frontend-js to Gradle kts (#2543)

* Kotlin DSL - rename "example-frontend-js" build script
* Kotlin DSL - 'example-frontend-js'
* Kotlin DSL - rename "play-services" build script
* Kotlin DSL - 'play-services'

Co-authored-by: Victor Turansky <victor.turansky@gmail.com>

integration/kotlinx-coroutines-play-services/build.gradle.kts

@@ -0,0 +1,41 @@
+/*
+ * Copyright 2016-2021 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
+ */
+
+val tasksVersion = "16.0.1"
+
+val artifactType = Attribute.of("artifactType", String::class.java)
+val unpackedAar = Attribute.of("unpackedAar", Boolean::class.javaObjectType)
+
+configurations.configureEach {
+    afterEvaluate {
+        if (isCanBeResolved) {
+            attributes.attribute(unpackedAar, true) // request all AARs to be unpacked
+        }
+    }
+}
+
+dependencies {
+    attributesSchema {
+        attribute(unpackedAar)
+    }
+
+    artifactTypes {
+        create("aar") {
+            attributes.attribute(unpackedAar, false)
+        }
+    }
+
+    registerTransform(UnpackAar::class.java) {
+        from.attribute(unpackedAar, false).attribute(artifactType, "aar")
+        to.attribute(unpackedAar, true).attribute(artifactType, "jar")
+    }
+
+    api("com.google.android.gms:play-services-tasks:$tasksVersion") {
+        exclude(group="com.android.support")
+    }
+}
+
+externalDocumentationLink(
+    url = "https://developers.google.com/android/reference/"
+)

js/example-frontend-js/build.gradle.kts

@@ -0,0 +1,27 @@
+/*
+ * Copyright 2016-2021 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
+ */
+
+kotlin {
+    js(LEGACY) {
+        binaries.executable()
+        browser {
+            distribution {
+                directory = directory.parentFile.resolve("dist")
+            }
+            commonWebpackConfig {
+                cssSupport.enabled = true
+            }
+            testTask {
+                useKarma {
+                    useChromeHeadless()
+                }
+            }
+        }
+    }
+}
+
+dependencies {
+    implementation("org.jetbrains.kotlinx:kotlinx-html-js:${version("html")}")
+    implementation(devNpm("html-webpack-plugin", "3.2.0"))
+}