Refactor handleStream to LLM Classes (#685)

server/utils/AiProviders/azureOpenAi/index.js

server/utils/AiProviders/gemini/index.js

server/utils/AiProviders/huggingface/index.js

server/utils/AiProviders/lmStudio/index.js

server/utils/AiProviders/localAi/index.js

server/utils/AiProviders/mistral/index.js

server/utils/AiProviders/native/index.js

server/utils/AiProviders/ollama/index.js

server/utils/AiProviders/openAi/index.js

server/utils/AiProviders/togetherAi/index.js

server/utils/chats/embed.js

server/utils/chats/stream.js