Qualcomm AI Engine Direct - LPBQ enablement (#9313)

### Summary
- QC backend changes for adopting LPBQ
- test case: conv2d 16a4w
- refactor a bit

### Test plan
```bash
python backends/qualcomm/tests/test_qnn_delegate.py -k TestQNNQuantizedOperator.test_qnn_backend_conv2d_block -s $SERIAL_NO -m SM8650 -b build-android
```