Allow storage() to work on python tensor subclasses, but error on future data accesses (#107417)
This was discussed in feedback from the original version of my "reorder proxy/fake" PR. This PR allows calls to `tensor.untyped_storage()` to **always** return a python storage object to the user. Previously, we would error loudly if we detected that the storage had a null dataptr.
Instead, I updated the python bindings for the python storage methods that I saw involve data access, to throw an error later, only if you try to access those methods (e.g. `storage.data_ptr()` will now raise an error if the data ptr is null).
Pull Request resolved: https://github.com/pytorch/pytorch/pull/107417
Approved by: https://github.com/albanD, https://github.com/ezyang, https://github.com/zou3519
