cli[minor]: Add first version of migrate (#20902)

Adds a first version of the migrate script.

libs/cli/tests/unit_tests/test_events.py

@@ -0,0 +1,7 @@
+from langchain_cli.utils.events import EventDict, create_events
+
+
+def test_create_events() -> None:
+    assert create_events(
+        [EventDict(event="Test Event", properties={"test": "test"})]
+    ) == {"status": "success"}