[PyTorch] Make TensorImpl::sizes() customizable and disable it for NestedTensorImpl (#73817)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/73817
NestedTensorImpl doesn't have sizes(). Silently getting wrong results back from it is not conducive to efficient software development. Make it throw while allowing sizes() to be inlined in the common case anyway, just like is_contiguous(). Thanks ezyang for the reminder that we could do this.
ghstack-source-id: 151302903
Test Plan: Updated test_nestedtensor.py
Reviewed By: ezyang
Differential Revision: D34660829
fbshipit-source-id: 1289f21127d6a8359893f9174f3c430a290f2c7f
(cherry picked from commit 7098b9fcfbd25a03bac19e1148426ff073810edd)
