chore: Handle overloaded error in anthropic streaming response

[narengogi]

Title:

• Anthropic throws errors DURING streaming

When receiving a streaming response via >SSE, it’s possible that an error can occur after returning a 200 response, in which case >error handling wouldn’t follow these standard mechanisms.
https://docs.anthropic.com/en/api/errors

Related Issues: (optional)

• Gateway error when processing non-200 model response #722

Note:
This change technically ignores the exception from anthropic during streaming and terminates the stream. But we're not losing any information, we're putting stop reason error (not openai compliant)
This is because if OpenAI stream has an exception it terminates abruptly and does not give an error chunk