Data-source objects for rows that end as failed tests are never disposed #7123

Summary

When a data-source row produces a test that then fails during test building (for example, generic type resolution or a generic constraint violation), the objects the row factory created are never tracked or disposed. Disposable data such as streams, connections or containers stays open until the process exits.

Where

• Reflection mode: the factory runs and its objects are initialized. Then the generic-resolution catch in the test builder adds a failed test and moves on, without registering those objects with the object tracker.
• Source-gen mode (with fix(engine): substitute class type arguments and array element types in build-time constraint checks #7102): GenericConstraintViolationDataSource runs each wrapped row factory, so that a factory exception wins over the constraint failure, and then discards the returned objects.

Expected

Objects created for a row that ends as a failed test are disposed (or tracked and disposed at session end), consistently in both modes. They should not be disposed blindly while something might still reference them, for example shared or keyed instances.

Notes

Raised by review bots on #7102 and #7112; deferred because it predates those PRs and needs an engine-wide change to how failed tests are built.