[Gradle] Fix possible CME in sourceSetsMetadataOutputs

Iterating over source sets and waiting for compilation wasn't safe.
 Because compilation upon configuration were able
 to add more source sets.

 Awaiting source sets first should solve the issue.

^KT-61652 Verification Pending

libraries/tools/kotlin-gradle-plugin/src/common/kotlin/org/jetbrains/kotlin/gradle/plugin/mpp/ProjectMetadataProviderImpl.kt

@@ -64,9 +64,7 @@ internal suspend fun Project.collectSourceSetMetadataOutputs(): Map<SourceSetNam
 }
 
 private suspend fun KotlinMultiplatformExtension.sourceSetsMetadataOutputs(): Map<KotlinSourceSet, FileCollection?> {
-    KotlinPluginLifecycle.Stage.AfterFinaliseDsl.await()
-
-    return sourceSets.associateWith { sourceSet ->
+    return awaitSourceSets().associateWith { sourceSet ->
         when (val compilation = project.findMetadataCompilation(sourceSet)) {
             null -> null
             is KotlinCommonCompilation -> compilation.output.classesDirs