fix deepcopy of lazy tree

[braingram]

Description

This fixes a bug where a deepcopy of a lazy node retains references to the original lazy tree (instead of becoming non-lazy nodes). While adding tests for and fixing this issue I found that walk_and_modify converts AsdfOrderedDictNode instances into dict. That bug is also fixed in this PR and is required for this PR since walk_and_modify is used to handle the deepcopy.

Tasks

• run pre-commit on your machine
• run pytest on your machine
• Does this PR add new features and / or change user-facing code / API? (if not, label with no-changelog-entry-needed)
  • write news fragment(s) in changes/: echo "changed something" > changes/<PR#>.<changetype>.rst (see below for change types)
  • update relevant docstrings and / or docs/ page
  • for any new features, add unit tests

news fragment change types...

• changes/<PR#>.feature.rst: new feature
• changes/<PR#>.bugfix.rst: bug fix
• changes/<PR#>.doc.rst: documentation change
• changes/<PR#>.removal.rst: deprecation or removal of public API
• changes/<PR#>.general.rst: infrastructure or miscellaneous change

[braingram]

Docs failed due to temporary unavailability of the astropy objects.inv needed for intersphinx links. EDIT: fixed by a rerun

[zacharyburnett]

should we also test multiple files open in context managers? To replicate the original issue (or was that using file handles)

[braingram]

Thanks! The original issue can be seen with the following example:

import gc
import roman_datamodels.datamodels as rdm
dst = rdm.ImageModel()
with rdm.open("some_cal.asdf") as src:
    dst.meta = src.meta.copy()
del src
gc.collect(2)
dst.meta.ref_file  # ok since the copy is shallow
dst.meta.ref_file.crds  # fails due to the sub node `crds` not being resolved (made not lazy) during the copy

With this PR that example runs without failure.
What did you have in mind for the multiple files?
I tried to flush out this test with a few "gotchas" (the recursive reference, etc) but it's far from exhaustive. Thanks for the idea!

[zacharyburnett]

this LGTM as far as I can tell