TensorExpr eval: fix copying variables from pointers on big endian systems (#96951)
When copying data from pointers, only lowest bytes are copied. On little endian systems they are located at the beginning of pointer. On big endian systems they are located at the end of pointer.
This change fixes TestTensorExprPyBind::test_dynamic_shape and TestTensorExprPyBind::test_dynamic_shape_2d tests from test/test_tensorexpr_pybind.py on big endian systems.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/96951
Approved by: https://github.com/ezyang, https://github.com/EikanWang
