[kpm] kgp-idea-proto: Create special binaryValidationApiElements configuration

This will be a 'lean' jar file (un-shadowed), which can later
be used by the binary-compatibility-validator to test the
API surface against.

^KT-52568 Verification Pending

libraries/tools/kotlin-gradle-plugin-idea-proto/build.gradle.kts

@@ -56,6 +56,21 @@ runtimeJar(tasks.register<ShadowJar>("shadowJar")) {
 
 publish()
 
+/* Setup configuration for binary compatibility tests */
+run {
+    val binaryValidationApiElements by configurations.creating {
+        isCanBeResolved = false
+        isCanBeConsumed = true
+    }
+
+    val binaryValidationApiJar = tasks.register<Jar>("binaryValidationApiJar") {
+        this.archiveBaseName.set(project.name + "-api")
+        from(mainSourceSet.output)
+    }
+
+    artifacts.add(binaryValidationApiElements.name, binaryValidationApiJar)
+}
+
 tasks.register<Exec>("protoc") {
     val protoSources = file("src/main/proto")
     val javaOutput = file("src/generated/java/")