[quant][better-engineering][bc-breaking] Removed quant_min/quant_max from fake_quant modules
Summary:
FakeQuantize class has quant_min/quant_max and activation_post_process
attributes, the latter of which already includes quant_min/max. As such,
we can remove quant_min/quant_max from FakeQuantize and use
FakeQuantize.activation_post_process.quant_m* directly.
Test plan:
```
python test/test_quantization.py
```
Pull Request resolved: https://github.com/pytorch/pytorch/pull/76674
Approved by: https://github.com/vkuzo
