test(etdump): Add FileDataSink test coverage (#9332)

test(etdump): Add FileDataSink test coverage

## Summary
Adds test validation for FileDataSink usage in ETDumpGen scenarios.
Extends existing debug event tests to cover file-based data sinks.

## Test Plan
**Build & Run Tests**:
```bash
# From build directory (cmake-out)
make -j32
ctest -R sdk_etdump_tests --output-on-failure
```

Fixes #9165

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Co-authored-by: root <root@en4230612l.fulton.ad.asu.edu>