Fix: Handle multiple tool calls in json to stream response handler

[VisargD]

In the OpenAIChatCompleteJSONToStreamResponseTransform function, we convert an OpenAI-like json response to stream response. But the function only considers the first tool call while creating stream chunks. This becomes an issue when there are more than 1 tool calls (parallel function calling) returned in response.

gateway/src/providers/openai/chatComplete.ts

Line 124 in 40d2365

const currentToolCall = choice.message.tool_calls[0];

Discord link where the issue was reported which led to this finding: https://discord.com/channels/1143393887742861333/1214959777566826536

Solution: Instead of parsing only 0 index for tool_calls, loop all tool calls and generate respective stream chunks