Build: Migrate stdlib & kotlin-test to maven-publish publication

libraries/stdlib/jdk8/build.gradle

@@ -3,8 +3,10 @@ description = 'Kotlin Standard Library JDK 8 extension'
 apply plugin: 'kotlin'
 
 configureJvm6Project(project)
-// TODO: Migrate to maven-publish publishing
-configureLegacyPublishing(project)
+configurePublishing(project)
+configureSourcesJar()
+configureJavadocJar()
+
 ext.javaHome = JDK_18
 ext.jvmTarget = "1.8"
 
@@ -44,15 +46,13 @@ jar {
     from sourceSets.java9.output
 }
 
-task modularJar(type: Jar) {
+configureModularJar {
     dependsOn(jar)
     manifestAttributes(manifest, project, 'Main', true)
-    classifier = 'modular'
 
     from zipTree(jar.outputs.files.singleFile)
 }
 
-
 artifacts {
     archives sourcesJar
     sources sourcesJar
@@ -60,8 +60,6 @@ artifacts {
     archives modularJar
 }
 
-configureJavadocJar()
-
 tasks.withType(org.jetbrains.kotlin.gradle.tasks.KotlinCompile) {
     kotlinOptions.jdkHome = JDK_18
     kotlinOptions.jvmTarget = 1.8