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

libraries/stdlib/jdk7/build.gradle

@@ -3,8 +3,10 @@ description = 'Kotlin Standard Library JDK 7 extension'
 apply plugin: 'kotlin'
 
 configureJvm6Project(project)
-// TODO: Migrate to maven-publish publishing
-configureLegacyPublishing(project)
+configurePublishing(project)
+configureSourcesJar()
+configureJavadocJar()
+
 ext.javaHome = JDK_17
 
 sourceSets {
@@ -50,10 +52,9 @@ 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)
 }
@@ -66,8 +67,6 @@ artifacts {
     archives modularJar
 }
 
-configureJavadocJar()
-
 tasks.withType(org.jetbrains.kotlin.gradle.tasks.KotlinCompile) {
     kotlinOptions.jdkHome = JDK_17
 }