[Gradle] Support Native embeddable compiler jar in subplugins

Apply generic (backend-agnostic) compiler plugin artifact instead of
Native-specific one when Native embeddable compiler jar is used
(with `kotlin.native.useEmbeddableCompilerJar=true` project property).

libraries/tools/kotlin-gradle-plugin-api/src/main/kotlin/org/jetbrains/kotlin/gradle/plugin/KotlinGradleSubplugin.kt

@@ -123,6 +123,14 @@ interface KotlinCompilerPluginSupportPlugin : Plugin<Project> {
 
     fun getCompilerPluginId(): String
     fun getPluginArtifact(): SubpluginArtifact
+
+    /**
+     * Kotlin/Native-specific plugin artifact.
+     *
+     * If Gradle is configured to use Kotlin/Native embeddable compiler jar
+     * (with `kotlin.native.useEmbeddableCompilerJar=true` project property),
+     * then [getPluginArtifact] is used instead.
+     */
     fun getPluginArtifactForNative(): SubpluginArtifact? = null
 }