JVM IR: support value classes only when feature is enabled

Remove NeedsToVisit because it doesn't really help with performance, and
it significantly increases code complexity.

compiler/backend/src/org/jetbrains/kotlin/codegen/optimization/boxing/BoxedBasicValue.kt

@@ -176,6 +176,8 @@ fun unboxedTypeOfInlineClass(boxedType: Type, state: GenerationState): Type? {
 }
 
 fun getMultiFieldValueClassUnboxInfo(boxedType: Type, state: GenerationState): MultiFieldValueClassUnboxInfo? {
+    if (!state.config.supportMultiFieldValueClasses) return null
+
     val descriptor =
         state.jvmBackendClassResolver.resolveToClassDescriptors(boxedType).singleOrNull()?.takeIf { it.isMultiFieldValueClass() }
             ?: return null

compiler/backend/src/org/jetbrains/kotlin/codegen/optimization/boxing/BoxingInterpreter.kt

@@ -297,7 +297,7 @@ private fun AbstractInsnNode.isInlineClassUnboxing(state: GenerationState) =
     }
 
 private fun AbstractInsnNode.isMultiFieldValueClassUnboxing(state: GenerationState) =
-    isMethodInsnWith(Opcodes.INVOKEVIRTUAL) {
+    state.config.supportMultiFieldValueClasses && isMethodInsnWith(Opcodes.INVOKEVIRTUAL) {
         isMultiFieldValueClassUnboxingMethodDescriptor(state)
     }
 

compiler/backend/src/org/jetbrains/kotlin/codegen/state/JvmBackendConfig.kt

@@ -100,4 +100,6 @@ class JvmBackendConfig(configuration: CompilerConfiguration) {
     val noNewJavaAnnotationTargets: Boolean = configuration.getBoolean(JVMConfigurationKeys.NO_NEW_JAVA_ANNOTATION_TARGETS)
 
     val oldInnerClassesLogic: Boolean = configuration.getBoolean(JVMConfigurationKeys.OLD_INNER_CLASSES_LOGIC)
+
+    val supportMultiFieldValueClasses: Boolean = languageVersionSettings.supportsFeature(LanguageFeature.ValueClasses)
 }