👷‍♂️ Conversations: Re-organize conversation code [Part 1]

[alchaplinsky]

Motivation

There's a bunch of conversation-related classes (eg. AIMessage, HumanMessage, ConversationMemory, etc.) that got added to Langchain root namespace. We should scope everything under Langchain::Conversation namespace. And also simplify class naming.

I personally don't think AIMessage and HumanMessage are good names. What if it is a conversation between LLMs? Than HumanMessage doesn't really make sense. It is better to stick to Prompt/Response pattern in naming different message classes even though under the hood Prompt will be sending {role: 'user'} to the API (that is an internal implementation so that's fine).

Changes

• Move conversation-related classes to lib/langchaing/conversation directory
• Rename class names:
  • ConversationMemory => Conversation::Memory
  • Message => Conversation::Message
  • HumanMessage => Conversation::Prompt
  • AIMessage => Conversation::Response
  • SystemMessage => Conversation::Context