Fix a compatibility issue with AnnotationDescriptor

The `getSourceForArgument` method should be in the interface,
but adding it is a breaking change for Java usages,
since the module is not built with -Xjvm-default (KT-54749).

Move the method to an extension. This doesn't change the behavior,
since it was only ever called on LazyAnnotationDescriptor.

buildSrc/src/main/kotlin/common-configuration.gradle.kts

@@ -288,4 +288,5 @@ fun skipJvmDefaultAllForModule(path: String): Boolean =
             //     java.lang.IllegalAccessError: tried to access method kotlin.reflect.jvm.internal.impl.types.checker.ClassicTypeSystemContext$substitutionSupertypePolicy$2.<init>(
             //       Lkotlin/reflect/jvm/internal/impl/types/checker/ClassicTypeSystemContext;Lkotlin/reflect/jvm/internal/impl/types/TypeSubstitutor;
             //     )V from class kotlin.reflect.jvm.internal.impl.resolve.OverridingUtilTypeSystemContext
+            // KT-54749
             path == ":core:descriptors"