shallow fold prevention for addr, nkHiddenAddr (#24322)

fixes #24305, refs #23807

Since #23014 `nkHiddenAddr` is produced to fast assign array elements in
iterators. However the array access inside this `nkHiddenAddr` can get
folded at compile time, generating invalid code. In #23807, compile time
folding of regular `addr` expressions was changed to be prevented in
`transf` but `nkHiddenAddr` was not updated alongside it.

The method for preventing folding in `addr` in #23807 was also faulty,
it should only trigger on the immediate child node of the address rather
than all nodes nested inside it. This caused a regression as outlined in
[this
comment](https://github.com/nim-lang/Nim/pull/24322#issuecomment-2419560182).

To fix both issues, `addr` and `nkHiddenAddr` now both shallowly prevent
constant folding for their immediate children.

tests/iter/tfoldedaddr.nim

@@ -0,0 +1,32 @@
+discard """
+  output: '''
+23
+23
+23
+23
+23
+23
+'''
+"""
+
+block: # issue #24305
+  iterator demo(a: openArray[int]): int =
+    for k in countUp(a[0], 19):
+      yield 23
+
+  for k in demo(@[17]):
+    echo k
+
+block: # issue #24305 with array
+  iterator demo(a: array[1, int]): int =
+    for k in countUp(a[0], 19):
+      yield 23
+
+  for k in demo([17]):
+    echo k
+
+block: # related regression
+  proc main =
+    let a = [0, 1, 2]
+    let x = addr a[low(a)]
+  main()