Qualcomm AI Engine Direct - qat proto

* [qat proto]

- Add qat proto
- Add Unit test test_qnn_backend_linear_qat
- Test command
```bash
python backends/qualcomm/tests/test_qnn_delegate.py -H $HOST -s $DEVICE -b $build-android/ -m "SM8650" -r $EXECUTORCH_ROOT -k TestQNNQuantizedOperator.test_qnn_backend_linear_qat
```

* [Fix lint]

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Co-authored-by: Joey Tsai <chunit@qti.qualcomm.com>

Pull Request resolved: https://github.com/pytorch/executorch/pull/6222