[quant][core][gpu][improvement] Removed linear_output and set output tensors as virtual in quantized cudnn linear op
Summary:
See https://github.com/pytorch/pytorch/pull/76787. Same idea applied
here but for `linear_output`.
Test plan:
```
python test/test_quantization.py --k test_qlinear_cudnn
```
Pull Request resolved: https://github.com/pytorch/pytorch/pull/77518
Approved by: https://github.com/jerryzh168
