fix(tests): bring back some responses tests (#4098)

#4055 cleaned the agents
implementation but while doing so it removed some tests which actually
corresponded to the responses implementation. This PR brings those tests
and assocated recordings back.

(We should likely combine all responses tests into one suite, but that
is beyond the scope of this PR.)

Author: ashwinb

tests/integration/agents/__init__.py

@@ -0,0 +1,5 @@
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+# All rights reserved.
+#
+# This source code is licensed under the terms described in the LICENSE file in
+# the root directory of this source tree.