Refactor TelegramChatLoader and FacebookChatLoader classes and add tests (#3863)

This PR includes two main changes:

- Refactor the `TelegramChatLoader` and `FacebookChatLoader` classes by
removing the dependency on pandas and simplifying the message filtering
process.

- Add test cases for the `TelegramChatLoader` and `FacebookChatLoader`
classes. This test ensures that the class correctly loads and processes
the example chat data, providing better test coverage for this
functionality.

tests/integration_tests/document_loaders/test_facebook_chat.py

@@ -0,0 +1,28 @@
+from pathlib import Path
+
+from langchain.document_loaders import FacebookChatLoader
+
+
+def test_facebook_chat_loader() -> None:
+    """Test FacebookChatLoader."""
+    file_path = Path(__file__).parent.parent / "examples/facebook_chat.json"
+    loader = FacebookChatLoader(str(file_path))
+    docs = loader.load()
+
+    assert len(docs) == 1
+    assert docs[0].metadata["source"] == str(file_path)
+    assert docs[0].page_content == (
+        "User 2 on 2023-02-05 13:46:11: Bye!\n\n"
+        "User 1 on 2023-02-05 13:43:55: Oh no worries! Bye\n\n"
+        "User 2 on 2023-02-05 13:24:37: No Im sorry it was my mistake, "
+        "the blue one is not for sale\n\n"
+        "User 1 on 2023-02-05 13:05:40: I thought you were selling the blue one!\n\n"
+        "User 1 on 2023-02-05 13:05:09: Im not interested in this bag. "
+        "Im interested in the blue one!\n\n"
+        "User 2 on 2023-02-05 13:04:28: Here is $129\n\n"
+        "User 2 on 2023-02-05 13:04:05: Online is at least $100\n\n"
+        "User 1 on 2023-02-05 12:59:59: How much do you want?\n\n"
+        "User 2 on 2023-02-05 08:17:56: Goodmorning! $50 is too low.\n\n"
+        "User 1 on 2023-02-05 00:17:02: Hi! Im interested in your bag. "
+        "Im offering $50. Let me know if you are interested. Thanks!\n\n"
+    )