more ORC bugfixes (#15355)

* introduced --define:nimArcIds

* ORC: bugfixes

tests/arc/tasyncleak3.nim

@@ -0,0 +1,46 @@
+discard """
+  cmd: "nim c --gc:orc $file"
+  output: "true"
+"""
+
+import strutils
+
+type
+  FutureBase* = ref object of RootObj  ## Untyped future.
+    finished: bool
+    stackTrace: seq[StackTraceEntry] ## For debugging purposes only.
+
+proc newFuture*(): FutureBase =
+  new(result)
+  result.finished = false
+  result.stackTrace = getStackTraceEntries()
+
+type
+  PDispatcher {.acyclic.} = ref object
+
+var gDisp: PDispatcher
+new gDisp
+
+proc testCompletion(): FutureBase =
+  var retFuture = newFuture()
+
+  iterator testCompletionIter(): FutureBase {.closure.} =
+    retFuture.finished = true
+    when not defined(nobug):
+      let disp = gDisp # even worse memory consumption this way...
+
+  var nameIterVar = testCompletionIter
+  proc testCompletionNimAsyncContinue() {.closure.} =
+    if not nameIterVar.finished:
+      discard nameIterVar()
+  testCompletionNimAsyncContinue()
+  return retFuture
+
+proc main =
+  for i in 0..10_000:
+    discard testCompletion()
+
+main()
+
+GC_fullCollect()
+echo getOccupiedMem() < 1024