Support for sambanova LLM provider

[Vaibhav-npc]

Checked

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Feature request

Implement support for the SambaNova provider in LangChain.js, mirroring the functionality available in the Python version of LangChain.

Motivation

Python langchain has sambanova provider, which js does not
https://python.langchain.com/docs/integrations/llms/sambanova/

Proposal (If applicable)

No response