[quant] Add imports to the torch/ao/quantization/__init__.py (#64911)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/64911
The import statements that involve the `quantize.py` were not added to the module level __init__ file. Those imports are necessary to mimic the behavior of the old import locations. Otherwise, the user would need to change their import statements to `from torch.ao.quantization.quantize import quantize` (instead of `from torch.ao.quantization import quantize`.
Another change in this diff is that we don't use `__all__` anymore. The all dunder was never used in quantization anyway, and just creates a potential bug when using `from ... import *`.
ghstack-source-id: 139342483
Test Plan: `buck test mode/dev //caffe2/test:quantization`
Reviewed By: vkuzo
Differential Revision: D30897663
fbshipit-source-id: a7b4919a191755e3ba690a79ce3362889f416689