Use swap_dims and set_index to rename xarray dims

The xarray team is currently deprecating how the
xarray.DataArray.rename() method works. Specifcally, renaming an
xarray.DataArray no longer creates an indexed coordinate. Using the
rename() method will generate the following warning for a given dimesion:

580: UserWarning: rename 't' to 't' does not create an index anymore. Try using swap_dims instead or use set_index after rename to create an indexed coordinate.
    return xarr.rename(dim_map)

This commit uses swap_dims() with set_index() to swap the
dimensions (i.e. rename them) and then reassert the indexed coordinates.

src/imagej/convert.py

@@ -577,7 +577,11 @@ def _rename_xarray_dims(xarr, new_dims: Sequence[str]):
     for i in range(xarr.ndim):
         dim_map[curr_dims[i]] = new_dims[i]
 
-    return xarr.rename(dim_map)
+    # swap dims and set indexed coordinates
+    coord_map = {v: k for k, v in dim_map.items()}
+    xarr = xarr.swap_dims(dim_map)
+
+    return xarr.set_index(coord_map)
 
 
 def _delete_labeling_files(filepath):