fix: reserve return pointer and RBP on stack for user func bodies

src/main/wacc/backend/Stack.scala

@@ -50,7 +50,7 @@ class Stack {
     * @param sizes
     *   The sizes of the values to reserve space for.
     */
-  def reserve(sizes: List[Size]): AsmLine = {
+  def reserve(sizes: Size*): AsmLine = {
     sizes.foreach { itemSize =>
       stack += stack.size -> StackValue(itemSize, sizeBytes)
     }