zero copy device support for integer fields

[cyrush]

We need to add logic for integer zero copy cases here:

ascent/src/libs/ascent/runtimes/ascent_vtkh_data_adapter.cpp

Line 1355 in 1f97a30

// we compile vtk-h with fp types

Otherwise, device only allocated fields will crash when we try to access on the host to convert them to floating point arrays here:

ascent/src/libs/ascent/runtimes/ascent_vtkh_data_adapter.cpp

Line 1379 in 1f97a30

n_vals.to_float64_array(n_tmp);

originally discussed here: #1100 (comment)

[cyrush]

Conduit Device support will make this easy, so we will wait for future Conduit release.