feat: adds test suite to verify provider's OAI compat endpoints (#1901)

# What does this PR do?


## Test Plan
pytest verifications/openai/test_chat_completion.py --provider together

tests/verifications/conftest.py

@@ -0,0 +1,28 @@
+# 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.
+
+
+def pytest_addoption(parser):
+    parser.addoption(
+        "--base-url",
+        action="store",
+        help="Base URL for OpenAI compatible API",
+    )
+    parser.addoption(
+        "--api-key",
+        action="store",
+        help="API key",
+    )
+    parser.addoption(
+        "--provider",
+        action="store",
+        help="Provider to use for testing",
+    )
+
+
+pytest_plugins = [
+    "tests.verifications.openai.fixtures.fixtures",
+]