[PyTorch] Extract parseOperator() into a standalone source file (#65179)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/65179
This is following up this PR: https://github.com/pytorch/pytorch/pull/61862. The purpose is to modularize operator parsing so that it can be used as needed without pulling the whole `import.cpp` into build.
Test Plan: Added a unit test in `test_lite_predictor.cpp` called `ParseOperators`, similar to `ParseBytecode`.
Reviewed By: iseeyuan
Differential Revision: D31006555
fbshipit-source-id: c38e221800af4cf72963a353c452c5437f56a0ac
