use shorter string for NOSTR value

[braingram]

The current NOSTR value used in the maker utils is incompatible with some archive_catalog nvarchar entries. Although this value likely shouldn't ever end up in the archive it prevents adding corresponding minLength keywords to the schemas (to check these nvarchars during schema validation).

This PR set's a new NOSTR value of ?. This was chosen as the smallest nvarchar value is 2 for visit_file_activity.

meta.filename requires a different value none as source_catalog will use this value for some unit tests:
https://github.com/spacetelescope/romancal/blob/96af8bbc6a6dafd48d1beb251b5209d9da875ca1/romancal/source_catalog/source_catalog_step.py#L151
Which then leads to a failure since it attempts to write to "?".

romancal also includes some of these default values in the doctests. spacetelescope/romancal#1419 is needed before this PR can be merged. EDIT: romancal PR is merged, rerunning regtests but will open this for review in case there are requested changes

Regression tests: https://github.com/spacetelescope/RegressionTests/actions/runs/10966346784
show same failures as main: https://github.com/spacetelescope/RegressionTests/actions/runs/10998102193

This PR is a requirement for spacetelescope/rad#448

Tasks

• update or add relevant tests
• update relevant docstrings and / or docs/ page
• Does this PR change any API used downstream? (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)
  • start a romancal regression test with this branch installed ("git+https://github.com/<fork>/roman_datamodels@<branch>")

news fragment change types...

• changes/<PR#>.feature.rst: new feature
• changes/<PR#>.bugfix.rst: fixes an issue
• changes/<PR#>.doc.rst: documentation change
• changes/<PR#>.removal.rst: deprecation or removal of public API
• changes/<PR#>.misc.rst: infrastructure or miscellaneous change

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.68%. Comparing base (087a60d) to head (7030feb).
Report is 88 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #388      +/-   ##
==========================================
+ Coverage   97.56%   97.68%   +0.12%     
==========================================
  Files          30       37       +7     
  Lines        2788     3372     +584     
==========================================
+ Hits         2720     3294     +574     
- Misses         68       78      +10     

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[PaulHuwe]

LGTM