Modify lazy_dyndep loading to trigger inside workspace. (#41687)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/41687
Specifically, this makes a new library (lazy), which can be used from both core
and workspace.
This allows workspace.Createnet to trigger lazy loading of dyndep dependencies.
Test Plan: Added a unit test specifically for workspace.CreateNet
Reviewed By: dzhulgakov
Differential Revision: D22441877
fbshipit-source-id: 3a9d1af9962585d08ea2566c9c85bec7377d39f2
