[FX] Make len traceable and scriptable with wrap (#50184)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/50184
Test Plan: Imported from OSS
Reviewed By: bertmaher
Differential Revision: D25819832
Pulled By: jamesr66a
fbshipit-source-id: ab16138ee26ef2f92f3478c56f0db1873fcc5dd0
