[reland][quant][test] Fix broken PT2 import, add warnings (#102819)
Summary:
We are currently silently skipping all PT2 quantization
tests due to a recent typo. This commit fixes this and also adds
warnings so it'll be easier to debug similar issues in the future.
Test Plan: python test/test_quantization.py
Differential Revision: D46383546
Pull Request resolved: https://github.com/pytorch/pytorch/pull/102819
Approved by: https://github.com/jerryzh168
