[PyTorch Mobile] Move some string ops to register_prim_ops.cpp and make them selective (#44500)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/44500
Some user models are using those operators. Unblock them while keep the ops selective.
Test Plan: CI
Reviewed By: linbinyu
Differential Revision: D23634769
fbshipit-source-id: 55841d1b07136b6a27b6a39342f321638dc508cd
