Remove NestedTensor from DefaultBackend alias (#54559)
Summary:
Kernels such as "add" are registered to DefaultBackend. At a minimum NestedTensor is not compatible with structured kernels due to missing fields such as size, which can therefore cause difficult to catch bugs when being passed into a function without a NestedTensor-specific kernel.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/54559
Reviewed By: ezyang
Differential Revision: D27283591
Pulled By: cpuhrsch
fbshipit-source-id: fad7c03ca3b2190f2f90039dd2872184e9bc5049
