fixes #21171; dynamic acyclic refs need to use dyn decRef (#21184)

* fixes #21171; dyn destructors for acyclic inherited  refs

* add a test

* Update compiler/liftdestructors.nim

tests/arc/t21184.nim

@@ -0,0 +1,77 @@
+discard """
+  matrix: "--mm:orc"
+"""
+
+import std/[with]
+
+type
+  Node* {.acyclic.} = ref object of RootObj
+    name: string
+    data: pointer
+    children: seq[Node]
+  TextNode = ref object of Node
+    text: string
+
+proc fakeEcho(s: string) =
+  if s.len < 0:
+    echo s
+
+proc newNode[T: Node](parent: Node): T =
+  new result
+  result.data = alloc0(250)
+  parent.children.add(result)
+
+proc newRootNode(): Node =
+  new result
+  result.data = alloc0(250)
+
+method printNode(node: Node) {.base.} =
+  fakeEcho node.name
+
+method printNode(node: TextNode) =
+  procCall printNode(Node(node))
+  fakeEcho node.text
+
+proc printChildren(node: Node) =
+  for child in node.children:
+    child.printNode()
+    printChildren(child)
+
+proc free(node: Node) =
+  for child in node.children:
+    free(child)
+  dealloc(node.data)
+
+template node(parent: Node, body: untyped): untyped =
+  var node = newNode[Node](parent)
+  with node:
+    body
+
+proc textNode(parent: Node, text: string) =
+  var node = newNode[TextNode](parent)
+  node.text = text
+
+template withRootNode(body: untyped): untyped =
+  var root = newRootNode()
+  root.name = "root"
+  with root:
+    body
+  root.printNode()
+  printChildren(root)
+  root.free()
+
+proc doTest() =
+  withRootNode:
+    node:
+      name = "child1"
+      node:
+        name = "child2"
+        node:
+          name = "child3"
+          textNode "Hello, world!"
+
+
+# bug #21171
+if isMainModule:
+  for i in 0..100000:
+    doTest()