community[minor]: Add solar embedding (#19761)

Solar is a large language model developed by
[Upstage](https://upstage.ai/). It's a powerful and purpose-trained LLM.
You can visit the embedding service provided by Solar within this pr.

You may get **SOLAR_API_KEY** from
https://console.upstage.ai/services/embedding
You can refer to more details about accepted llm integration at
https://python.langchain.com/docs/integrations/llms/solar.