speed up and re-enable quantized bn unit tests (#37420)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/37420
The quantized BN unit tests were disabled because they took too long.
This diff removes hypothesis from these test cases and instead generates
the cases manually. The run time is ~7 seconds per test on my devgpu.
Test Plan:
```
python test/test_quantization.py TestQuantizedOps.test_batch_norm2d_relu
python test/test_quantization.py TestQuantizedOps.test_batch_norm3d
```
Imported from OSS
Differential Revision: D21310333
fbshipit-source-id: 2499f7a3d6a87c0278d012ae65132f148cee6d2e
