[3/N] Update ema_teacher_arch in the backward call (#92080)
Summary: adding support for updating ema_teacher_arch in C2 backend
Test Plan:
baseline
f397096610
EMA run
f397096864
Differential Revision: D41124891
Pull Request resolved: https://github.com/pytorch/pytorch/pull/92080
Approved by: https://github.com/kit1980
