[Issue #46210] added torch.fx.len() to provide support for len(); added a test case for torch.fx.len() (#49532)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/49532
Test Plan: Imported from OSS
Reviewed By: jamesr66a
Differential Revision: D25608804
Pulled By: huiguoo
fbshipit-source-id: 93ac02ab57db5d200d92443062286c34782ec0ef
