Add helper method to generate missing debug handles (#5902)

Summary:
Pull Request resolved: https://github.com/pytorch/executorch/pull/5902

Helper function to generate missing debug handles on nodes, which is usually needed when graph transforms are done and new nodes are inserted.

Reviewed By: Vysarat

Differential Revision: D63913905

fbshipit-source-id: 0a24afa1d5207356a2706db88ff7828a5fba7f1a