[reland] Call jit decomposition in VariableType to increase forward AD coverage (#84151) (#84675)
This reverts commit acb4a09628284201281e262aaee58e3dc6be9c2b.
In addition, we also fix a memory leak in layer norm.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/84675
Approved by: https://github.com/zou3519
