Preserve synthetic enum methods in stub-based 'ClsClassImpl'

'ClsClassImpl' instances created by the platform contain synthetic
enum methods (added by 'ClassInnerStuffCache.calcMethods()'). Such
convention is common in IntelliJ (see KT-36095 and
'9a8b345adaded83fe13980a28db5d9f9acc7450d' in the IntelliJ repository).

This commit makes Kotlin's stub-based classes consistent with the
convention. Instead, a filter is added in place of 'ClsClassImpl' usage.

See also the following commits:
- 7c86911f44
- 43468c6d55

analysis/decompiled/light-classes-for-decompiled/src/org/jetbrains/kotlin/analysis/decompiled/light/classes/KtLightClassForDecompiledDeclaration.kt

@@ -18,6 +18,7 @@ import org.jetbrains.kotlin.analyzer.KotlinModificationTrackerService
 import org.jetbrains.kotlin.asJava.classes.KotlinClassInnerStuffCache
 import org.jetbrains.kotlin.asJava.classes.LightClassesLazyCreator
 import org.jetbrains.kotlin.asJava.classes.lazyPub
+import org.jetbrains.kotlin.asJava.isSyntheticValuesOrValueOfMethod
 import org.jetbrains.kotlin.load.java.structure.LightClassOriginKind
 import org.jetbrains.kotlin.psi.KtClassOrObject
 
@@ -155,7 +156,8 @@ open class KtLightClassForDecompiledDeclaration(
 
     private val _methods: MutableList<PsiMethod> by lazyPub {
         mutableListOf<PsiMethod>().also {
-            clsDelegate.methods.mapTo(it) { psiMethod ->
+            clsDelegate.methods.mapNotNullTo(it) { psiMethod ->
+                if (isSyntheticValuesOrValueOfMethod(psiMethod)) return@mapNotNullTo null
                 KtLightMethodForDecompiledDeclaration(
                     funDelegate = psiMethod,
                     funParent = this,