Coordinates implicitly created when passing a DataArray as coord to Dataset constructor

I stumbled on this while working on #5692. Is this intended behavior or unwanted side effect?

What happened:

Create a new Dataset by passing a DataArray object as coordinate also add the DataArray coordinates to the dataset:

>>> foo = xr.DataArray([1.0, 2.0, 3.0], coords={"x": [0, 1, 2]}, dims="x")
>>> ds = xr.Dataset(coords={"foo": foo})
>>> ds
<xarray.Dataset>
Dimensions:  (x: 3)
Coordinates:
  * x        (x) int64 0 1 2
    foo      (x) float64 1.0 2.0 3.0
Data variables:
    *empty*

What you expected to happen:

The behavior above seems a bit counter-intuitive to me. I would rather expect no additional coordinates auto-magically added to the dataset, i.e. only one foo coordinate in this example:

>>> ds
<xarray.Dataset>
Dimensions:  (x: 3)
Coordinates:
    foo      (x) float64 1.0 2.0 3.0
Data variables:
    *empty*

Environment:

Start at the Dataset constructor path that handles a DataArray supplied through coords, using the reproduction in the issue to trace how the DataArray's own coordinates are incorporated. Add a regression test for this example and verify that constructing the Dataset leaves only the foo coordinate, without adding x separately.