Implement static_getitem for DpnpNdArray type

[diptorupd]

An implementation for the static_getitem function for DpnpNdArray is missing and that results in the lowering falling back to the generic lower_getitem that in turn resolves to the getitem_arraynd_intp call defined in numba/np/arrayobj.py.

In current main using Numba's function for DpnpNdArray works fine as the underlying data model for DpnpNdArray is the same as types.Array. However, with the changes introduced in #1083 the approach fails. Hence, we need a DpnpNdArray-specific implementation of getitem.