Support for default dtype in numba_dpex.local.array and numba_dpex.private.array

[samaid]

Currently dtype must be specified explicitly:

b = ndpx.local.array(ls, dtype=a.dtype)
c = ndpx.private.array(ls, dtype=a.dtype)

For consistency with dpnp need to support the case b = ndpx.local.array(ls) c = ndpx.private.array(ls)