concat() loads dask arrays if the first array is numpy

[crusaderky]

duck_array_ops.concatenate and duck_array_ops.stack load dask variables if the first one is numpy-based:

xarray.concat([
    xarray.DataArray([1]).chunk(),
    xarray.DataArray([1]),
], dim='dim_0')

Out[1]:
<xarray.DataArray (dim_0: 2)>
dask.array<shape=(2,), dtype=int64, chunksize=(1,)>
Dimensions without coordinates: dim_0

xarray.concat([
    xarray.DataArray([1]),
    xarray.DataArray([1]).chunk(),
], dim='dim_0')

Out[2]:
<xarray.DataArray (dim_0: 2)>
array([1, 1])
Dimensions without coordinates: dim_0