IR text tests: Unmute enum class-related tests

Making enum class-related tests unmuted requires implementing
a special "compatibility" mode for IR tree dumper to filter out
fake override declarations leaking from java.enum.Enum and
kotlin.Enum (JVM-only) classes.

compiler/testData/ir/irText/classes/enumEntries.sig.kt.txt

@@ -29,12 +29,6 @@ enum class MyEnum : Enum<MyEnum> {
   //   Public signature debug description: values#static(){}kotlin.Array<MyEnum>
   fun values(): Array<MyEnum>
 
-  // CHECK JVM_IR:
-  //   Mangled name: MyEnum#clone(){}kotlin.Any
-  //   Public signature: /MyEnum.clone|-6903128697527593263[0]
-  //   Public signature debug description: clone(){}kotlin.Any
-  protected /* fake */ override fun clone(): Any
-
   // CHECK JVM_IR:
   //   Mangled name: MyEnum#compareTo(MyEnum){}kotlin.Int
   //   Public signature: /MyEnum.compareTo|2015858924903177055[0]