move batchnorm and layernorm fusion to decompose (#20337)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/20337
ghimport-source-id: 2196f84f2ef384c1f25587b2fb4bd9dd2f63c2b4
Differential Revision: D15448596
Pulled By: wanchaol
fbshipit-source-id: b66e608f1b72471fc0775aaa4e09f9fa1070fc3c
