[PT2E][Quant][BE] Move pt2e quantization test to separate folder (#99064)
Move it out of fx for better code organizations
Differential Revision: [D44918496](https://our.internmc.facebook.com/intern/diff/D44918496/)
**NOTE FOR REVIEWERS**: This PR has internal Meta-specific changes or comments, please review them on [Phabricator](https://our.internmc.facebook.com/intern/diff/D44918496/)!
Pull Request resolved: https://github.com/pytorch/pytorch/pull/99064
Approved by: https://github.com/jerryzh168
