docs(samples): add samples to create/delete featurestore (googleapis#980

)

* feat: SDK feature store samples (create/delete fs)

* feat: adding to conftest.py

* docs(samples): fixed testing

* docs(samples): fixed testing

* docs(samples): fixed testing

* docs(samples) added changes

* docs(samples): style issues

* Update samples/model-builder/create_featurestore_sample_test.py

Co-authored-by: Morgan Du <morgandu@google.com>

* Update samples/model-builder/test_constants.py

Co-authored-by: Morgan Du <morgandu@google.com>

* Update samples/model-builder/create_featurestore_sample_test.py

Co-authored-by: Morgan Du <morgandu@google.com>

Co-authored-by: Morgan Du <morgandu@google.com>

samples/model-builder/conftest.py

@@ -387,9 +387,12 @@ def mock_get_featurestore(mock_featurestore):
 
 
 @pytest.fixture
-def mock_create_featurestore():
-    with patch.object(aiplatform.Featurestore, "create") as mock:
-        yield mock
+def mock_create_featurestore(mock_featurestore):
+    with patch.object(
+        aiplatform.featurestore.Featurestore, "create"
+    ) as mock_create_featurestore:
+        mock_create_featurestore.return_value = mock_featurestore
+        yield mock_create_featurestore
 
 
 @pytest.fixture