Update optimize_for_mobile to preserve node's debug information (#63106)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/63106
Propagate debug info to the re-written nodes in the graph.
Test Plan:
- Clone open source repo and build
- ``` python3 test/test_jit.py TestOptimizeForMobilePreserveDebugInfo ```
- Tests pass
Reviewed By: kimishpatel
Differential Revision: D28654659
fbshipit-source-id: 2d7c87f2fb95a3be53246375f35639bbd97c237e
