IntelPython / dpnp / 31689450687

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Fix abort in `top_k` for k=0 (#3022)

`dpnp.tensor.top_k(x, 0)` might aborted the process on an
assertions-enabled SYCL runtime:

```python
import dpnp.tensor as dpt
dpt.top_k(dpt.arange(12).reshape(3, 4), 0)   # k = 0
```

`k == 0` is a valid request whose result is empty, and it passes
validation (`k < 0` is rejected, `k > size` is rejected, but `k == 0` is
allowed). `py_topk` then dispatched to the kernel, whose output-writing
step (`write_out_impl`) builds an `nd_range` from `nelems = iter_nelems
* k`. A zero-sized `nd_range` is a silent no-op on runtimes built with
`NDEBUG`, but aborts on an assertions-enabled SYCL runtime.

The existing guard covered `iter_nelems == 0` and `axis_nelems == 0`,
but not `k == 0`.

This PR proposes to extend the early-return guard in `py_topk` to also
cover `k == 0`.

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