Use Plugins DSL in Kotlin Gradle scripts

When plugins DSL is used, there is no need to
manually generate typesafe accessors for extensions and
conventions (by running `./gradlew kotlinDslAccessorsSnapshot`).

ultimate/build.gradle.kts

@@ -4,8 +4,8 @@ import org.gradle.jvm.tasks.Jar
 
 description = "Kotlin IDEA Ultimate plugin"
 
-apply {
-    plugin("kotlin")
+plugins {
+    kotlin("jvm")
 }
 
 val ideaProjectResources =  project(":idea").the<JavaPluginConvention>().sourceSets["main"].output.resourcesDir

ultimate/ultimate-runner/build.gradle.kts

@@ -1,5 +1,7 @@
 
-apply { plugin("kotlin") }
+plugins {
+    kotlin("jvm")
+}
 
 dependencies {
     compileOnly(project(":idea"))