Deprecate TensorDictFeatureStore in cuGraph-PyG (#160)

First step in handling #159 .  The unified API will store all data in WholeGraph, which has superior performance and lower memory usage.  `TensorDictFeatureStore` is no longer a useful alternative.

Authors:
  - Alex Barghi (https://github.com/alexbarghi-nv)

Approvers:
  - Tingyu Wang (https://github.com/tingyu66)

URL: #160

Author: alexbarghi-nv

python/cugraph-pyg/cugraph_pyg/data/__init__.py

@@ -18,11 +18,22 @@
 )
 from cugraph_pyg.data.graph_store import GraphStore
 from cugraph_pyg.data.feature_store import (
-    TensorDictFeatureStore,
+    TensorDictFeatureStore as DEPRECATED__TensorDictFeatureStore,
     WholeFeatureStore,
 )
 
 
+def TensorDictFeatureStore(*args, **kwargs):
+    warnings.warn(
+        "TensorDictFeatureStore is deprecated.  Consider changing your "
+        "workflow to launch using 'torchrun' and store data in "
+        "the faster and more memory-efficient WholeFeatureStore instead.",
+        FutureWarning,
+    )
+
+    return DEPRECATED__TensorDictFeatureStore(*args, **kwargs)
+
+
 def DaskGraphStore(*args, **kwargs):
     warnings.warn(
         "DaskGraphStore and the Dask API are deprecated."