ALWAYS_SPLIT seems necessary for ZFP

At least these tests:

```
FAILED tests/ndarray/test_lossy.py::test_lossy[shape1-float64-cparams1-None-False] - RuntimeError: Error while creating the NDArray
FAILED tests/ndarray/test_lossy.py::test_lossy[shape3-float32-cparams3-lossy.b2nd-False] - RuntimeError: Error while creating the NDArray
```

fail if "splitmode" is set to`AUTO_SPLIT`, which is the new default after [this discussion](https://github.com/Blosc/python-blosc2/discussions/337).

Perhaps this is due to the design of the test, but while we can investigate more, they are set explicitly in the test to `ALWAYS_SPLIT`.