fix: update metatype tests for v5

[ehennestad]

Summary

• Update MetaTypeTest/testMetaType to exercise openMINDS v5 DatasetVersion properties and type mappings.
• Replace the removed mustBeSpecifiedLength validator test with coverage for mustBeMinLength and mustBeMaxLength.
• Simplify scalar property detection to use the current mustBeScalarOrEmpty validator.

Root Cause

The test still asserted v4 DatasetVersion properties such as author, while v5 uses contribution and mixed linked properties such as digitalIdentifier and usageCondition. The scalar-detection helper also still looked for the removed mustBeSpecifiedLength validator.

Validation

runtests('ommtest.internal.MetaTypeTest')
runtests('PropertyValidatorTest')