IR: change acceptChildren/transformChildren order in IrClass

Traverse properties of supertypes first, and then handle thisReceiver.
This will simplify transition to auto-generated IR.

compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/declarations/IrClass.kt

@@ -46,14 +46,14 @@ abstract class IrClass :
         visitor.visitClass(this, data)
 
     override fun <D> acceptChildren(visitor: IrElementVisitor<Unit, D>, data: D) {
-        thisReceiver?.accept(visitor, data)
         typeParameters.forEach { it.accept(visitor, data) }
         declarations.forEach { it.accept(visitor, data) }
+        thisReceiver?.accept(visitor, data)
     }
 
     override fun <D> transformChildren(transformer: IrElementTransformer<D>, data: D) {
-        thisReceiver = thisReceiver?.transform(transformer, data)
         typeParameters = typeParameters.transformIfNeeded(transformer, data)
         declarations.transformInPlace(transformer, data)
+        thisReceiver = thisReceiver?.transform(transformer, data)
     }
 }