Reading wrong binary from device

[josevalim]

If you wrap the contents of this test in a for:

https://github.com/elixir-nx/exla/blob/main/test/exla/nx_device_test.exs#L4

Like this:

  test "transfers data from nx<->device" do
    for _ <- 1..10000 do
    t = Nx.tensor([1, 2, 3, 4])

Then it fails with a 100% certainty for me. I think we are doing either one of:

1. When sending data to the device, we are using zero-copy (which we shouldn't, we should only do zero-copy on run, since we know the binary can't be GCed meanwhile)

2. When reading the data for a CPU device, we are pointing to a place in memory instead of allocating an Erlang binary (unlikely?)