IC mangling: Replace compiler hack with configuration flag

compiler/serialization/src/org/jetbrains/kotlin/serialization/DescriptorSerializer.kt

@@ -362,7 +362,7 @@ class DescriptorSerializer private constructor(
             }
 
             if (descriptor.hasInlineClassTypesInSignature()) {
-                if (descriptor.fqNameSafe.startsWith(Name.identifier("kotlin"))) {
+                if (extension.useOldInlineClassesManglingScheme()) {
                     builder.addVersionRequirement(writeVersionRequirement(LanguageFeature.InlineClasses))
                 } else {
                     builder.addVersionRequirement(

compiler/serialization/src/org/jetbrains/kotlin/serialization/SerializerExtension.kt

@@ -94,4 +94,6 @@ abstract class SerializerExtension {
     }
 
     open fun releaseCoroutines(): Boolean = false
+
+    open fun useOldInlineClassesManglingScheme(): Boolean = false
 }