feat: add read signed url of the vector chunks

[mnvsk97]

• Add a function to fetch artifacts of the data directory by data dir fqn.
• Add function to get read signed URL of a data dir and local file path
• Add read_signed_url along with the file chunk during ingestion to the vector database. This signed URL can be used in the QA response to provide a source file reference to the user on UI.
• Refactor MultiModalParser
  • Move default multi-modal parser prompt to constants
  • Move LLM instance creation to __init__
  • Remove unnecessary passing of instance objects like prompt, and llm between functions and use instance vars instead.
• Upgrade langchain-openai from 0.1.20 to 0.1.25 to fix issues introduced in this PR
• Remove unused libraries: openai and orjson