[const_fold] Keep around node.meta for replaced folded ops (#64782)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/64782
Previously, get_attrs that were added to the graph did not retain node.meta after folding. Add such support, and improve coverage in general here.
Test Plan: Added test coverage.
Reviewed By: protonu
Differential Revision: D30852704
fbshipit-source-id: ece87a61c69b2e68982964c6adc4dde14dae12c7
