[ty_test] Refactor: rename diagnostic.rs to check_output.rs
SortedDiagnostics is now replaced by SortedCheckOutputs, which handles
both diagnostics and hover results. This refactoring:
- Renames diagnostic.rs to check_output.rs to better reflect its purpose
- Moves CheckOutput and SortedCheckOutputs definitions from matcher.rs
to check_output.rs where they belong
- Removes the now-unused SortedDiagnostics infrastructure
- Ports the test to use SortedCheckOutputs instead of SortedDiagnostics
- Updates all imports throughout the codebase
The check_output module now serves as the central location for sorting
and grouping all types of check outputs (diagnostics and hover results)
by line number.
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Co-Authored-By: Claude <noreply@anthropic.com>
