add s3 protocol tests (#2667)

Author: lucix-aws

.changelog/76710fee76664e76989335824a2df29f.json

@@ -0,0 +1,8 @@
+{
+    "id": "76710fee-7666-4e76-9893-35824a2df29f",
+    "type": "bugfix",
+    "description": "Add S3-specific smithy protocol tests.",
+    "modules": [
+        "service/s3"
+    ]
+}