Refactor ObjectView validation

[ehennestad]

Motivation

Fix ObjectView validation, using similar strategies as for validation of SoftLinks.

Changes:

• Validate ObjectView and the target type.
• Allow specifying a target type directly (and wrap it in an ObjectView type internally)

How to test the behavior?

Show here how to reproduce the new behavior (can be a bug fix or a new feature)

Checklist

• Have you ensured the PR description clearly describes the problem and solutions?
• Have you checked to ensure that there aren't other open or previously closed Pull Requests for the same change?
• If this PR fixes an issue, is the first line of the PR description fix #XX where XX is the issue number?

[codecov]

Codecov Report

❌ Patch coverage is 91.22807% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 94.96%. Comparing base (6530e80) to head (4d3ec03).
⚠️ Report is 23 commits behind head on main.

Files with missing lines	Patch %	Lines
+types/+util/validateReferenceType.m	80.00%	3 Missing ⚠️
+file/fillValidators.m	95.23%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #739      +/-   ##
==========================================
- Coverage   94.99%   94.96%   -0.03%     
==========================================
  Files         169      170       +1     
  Lines        5993     6017      +24     
==========================================
+ Hits         5693     5714      +21     
- Misses        300      303       +3     

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