std/var functions raise TypeError when due to dtype casting

[antonwolfy]

The below example behaves differently in numpy and dpnp:

import dpnp, numpy

dpnp.__version__
# Out: '0.17.0dev6+6.g5b3beb35ee4'

numpy.__version__
# Out: '2.2.2'

a = dpnp.array([[1, 2], [3, 4]])

dpnp.var(a, dtype='i2')
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
Cell In[3], line 1
----> 1 dpnp.var(a, dtype='i2')

File /localdisk/work/antonvol/code/dpnp/dpnp/dpnp_iface_statistics.py:1758, in var(a, axis, dtype, out, ddof, keepdims, where, mean, correction)
   1755     result = dpnp.get_result_array(usm_res, out)
   1757 if out is None and dtype is not None:
-> 1758     result = result.astype(dtype, casting="same_kind")
   1759 return result

File /localdisk/work/antonvol/code/dpnp/dpnp/dpnp_array.py:853, in dpnp_array.astype(self, dtype, order, casting, subok, copy, device)
    848 if subok is not True:
    849     raise NotImplementedError(
    850         f"subok={subok} is currently not supported"
    851     )
--> 853 return dpnp.astype(
    854     self, dtype, order=order, casting=casting, copy=copy, device=device
    855 )

File /localdisk/work/antonvol/code/dpnp/dpnp/dpnp_iface.py:266, in astype(x1, dtype, order, casting, copy, device)
    263     order = "K"
    265 x1_obj = dpnp.get_usm_ndarray(x1)
--> 266 array_obj = dpt.astype(
    267     x1_obj, dtype, order=order, casting=casting, copy=copy, device=device
    268 )
    270 if array_obj is x1_obj and isinstance(x1, dpnp_array):
    271     # return x1 if dpctl returns a zero copy of x1_obj
    272     return x1

File /localdisk/work/antonvol/soft/miniforge3/envs/dpnp_dev_numpy20/lib/python3.12/site-packages/dpctl/tensor/_copy_utils.py:667, in astype(usm_ary, newdtype, order, casting, copy, device)
    664     target_dtype = _get_dtype(newdtype, usm_ary.sycl_queue)
    666 if not dpt.can_cast(ary_dtype, target_dtype, casting=casting):
--> 667     raise TypeError(
    668         f"Can not cast from {ary_dtype} to {newdtype} "
    669         f"according to rule {casting}."
    670     )
    671 c_contig = usm_ary.flags.c_contiguous
    672 f_contig = usm_ary.flags.f_contiguous

# but works with numpy:
na = a.asnumpy()

numpy.var(na, dtype='i2')
# Out: np.int16(1)