Langchain integration (#512)

* Added LangChain integration

* Fixed issue created by git checkin process

* Added ':' to characters to remove from end of file path

* Tested initial migration to LangChain, removed comments and logging used for debugging

* Tested initial migration to LangChain, removed comments and logging used for debugging

* Converted camelCase to snake_case

* Turns out we need the exception handling

* Testing Hugging Face Integrations via LangChain

* Added LangChain loadable models

* Renames "qa" prompt to "clarify", since it's used in the "clarify" step, asking for clarification

* Fixed loading model yaml files

* Fixed streaming

* Added modeldir cli option

* Fixed typing

* Fixed interaction with token logging

* Fix spelling + dependency issues + typing

* Fix spelling + tests

* Removed unneeded logging which caused test to fail

* Cleaned up code

* Incorporated feedback

- deleted unnecessary functions & logger.info
- used LangChain ChatLLM instead of LLM to naturally communicate with gpt-4
- deleted loading model from yaml file, as LC doesn't offer this for ChatModels

* Update gpt_engineer/steps.py

Co-authored-by: Anton Osika <anton.osika@gmail.com>

* Incorporated feedback

- Fixed failing test
- Removed parsing complexity by using # type: ignore
- Replace every ocurence of ai.last_message_content with its content

* Fixed test

* Update gpt_engineer/steps.py

---------

Co-authored-by: H <holden.robbins@gmail.com>
Co-authored-by: Anton Osika <anton.osika@gmail.com>

tests/test_collect.py

@@ -43,7 +43,7 @@ def test_collect_learnings(monkeypatch):
     b = {k: v for k, v in learnings.to_dict().items() if k != "timestamp"}
     assert a == b
 
-    assert code in learnings.logs
+    assert json.dumps(code) in learnings.logs
     assert code in learnings.workspace