[FX] Speed up _Namespace.create_name (#55580)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/55580
Test Plan: Imported from OSS
Reviewed By: ansley
Differential Revision: D27641156
Pulled By: jamesr66a
fbshipit-source-id: d2443d41c8d84dddb1794a7901e2d09ae3639846
