Multiple LLM Support framework + AzureOpenAI Support (#180)

* Remove LangchainJS for chat support chaining
Implement runtime LLM selection
Implement AzureOpenAI Support for LLM + Emebedding
WIP on frontend
Update env to reflect the new fields

* Remove LangchainJS for chat support chaining
Implement runtime LLM selection
Implement AzureOpenAI Support for LLM + Emebedding
WIP on frontend
Update env to reflect the new fields

* Replace keys with LLM Selection in settings modal
Enforce checks for new ENVs depending on LLM selection