[WIP] add explicit dynamic fusion arg (#71173)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/71173
Test Plan: Imported from OSS
Reviewed By: navahgar
Differential Revision: D33536222
Pulled By: eellison
fbshipit-source-id: a097408ecdd6e284432de128feb297993d882d52
(cherry picked from commit 0e3419b2d32e798539a35db9c47aa85f7487a524)
