IR: IrTypeAlias: serialize/deserialize new IR objects

Add uniqId for typealias declarations.
Implement WrappedTypeAliasDescriptor.

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

@@ -452,6 +452,8 @@ class DescriptorSerializer private constructor(
             builder.addAnnotation(extension.annotationSerializer.serializeAnnotation(annotation))
         }
 
+        extension.serializeTypeAlias(descriptor, builder)
+
         return builder
     }
 

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

@@ -83,6 +83,9 @@ abstract class SerializerExtension {
     open fun serializeTypeParameter(typeParameter: TypeParameterDescriptor, proto: ProtoBuf.TypeParameter.Builder) {
     }
 
+    open fun serializeTypeAlias(typeAlias: TypeAliasDescriptor, proto: ProtoBuf.TypeAlias.Builder) {
+    }
+
     open fun serializeErrorType(type: KotlinType, builder: ProtoBuf.Type.Builder) {
         throw IllegalStateException("Cannot serialize error type: $type")
     }

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

@@ -106,4 +106,10 @@ abstract class KotlinSerializerExtensionBase(private val protocol: SerializerExt
             proto.addExtension(protocol.typeParameterAnnotation, annotationSerializer.serializeAnnotation(annotation))
         }
     }
+
+    override fun serializeTypeAlias(typeAlias: TypeAliasDescriptor, proto: ProtoBuf.TypeAlias.Builder) {
+        // TODO serialize annotations on type aliases?
+        // (this requires more extensive protobuf scheme modifications)
+    }
+
 }