[ty_test] Simplify unmatched output handling
Implement UnmatchedWithColumn for CheckOutput and update the column()
method to work with CheckOutput instead of just Diagnostic.
This allows eliminating the match statement when formatting unmatched
outputs - we can now just call unmatched_with_column() on all outputs
uniformly.
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Co-Authored-By: Claude <noreply@anthropic.com>
