pippy tracer ignores 'non_persistent' attribute of buffers

[wconstab]

Fixing this issue depends on also first fixing https://github.com/pytorch/pytorch/issues/123411 so that the original 'split_graph' retains the 'non_persistent' attribute.

            if is_buffer:
                _assign_attr(
                    param_val,
                    callee,
                    param_fqn,
                    attr_kind=_AttrKind.BUFFER,
                    persistent=True,                #  <------------- This value should not be hardcoded
                )
            else:
                _assign_attr(
                    param_val,
                    callee,
                    param_fqn,
                    attr_kind=_AttrKind.PARAMETER,
                )