Add multi-variable rechunking (#1546)

tests/geospatial/test_rechunking.py

@@ -13,10 +13,17 @@ def test_era5_rechunking(client, gcs_url, scale):
     if scale == "small":
         # 101.83 GiB (small)
         time_range = slice("2020-01-01", "2023-01-01")
+        variables = ["sea_surface_temperature"]
+    elif scale == "medium":
+        # 2.12 TiB (medium)
+        time_range = slice(None)
+        variables = ["sea_surface_temperature"]
     else:
-        # 2.12 TiB (large)
+        # 4.24 TiB (large)
+        # This currently doesn't complete successfully.
         time_range = slice(None)
-    subset = ds.sea_surface_temperature.sel(time=time_range)
+        variables = ["sea_surface_temperature", "snow_depth"]
+    subset = ds[variables].sel(time=time_range)
 
     # Rechunk
     result = subset.chunk({"time": -1, "longitude": "auto", "latitude": "auto"})