Update TigerRag Langchain Folder to Make it Match Newest Movie_Recs Logic

[wendyran]

Morive_recs overall logic has been updated, and major functions are modularized.
e.g.

• https://github.com/tigerlab-ai/tiger/blob/main/TigerRag/tigerrag/base/models.py#L27
• https://github.com/tigerlab-ai/tiger/blob/main/TigerRag/tigerrag/rag/retrieval_augmenters.py#L6

Update langchain folder code, so that it is calling the modularized functions directly, instead of redefining the functions.

[gjyotin305]

@wendyran I would like to take this issue

[tigerlab-ai]

Hi @gjyotin305 , thank for contributing! Please don't hesitate to create a pull request, and we will promptly review it. Your efforts are greatly appreciated!