language_models: Add OpenRouterError and map OpenRouter errors to LanguageModelCompletionError (#34227)

Improves the error handling for openrouter and adds automatic retry like
anthropic for few of the status codes.
Release Notes:

- Improves error messages for Openrouter provider
- Automatic retry when rate limited or Server error from Openrouter
4368c1b56bUmesh Yadav committed on 9/2/2025, 11:13:46 PM· committed by GitHubparente5a968b
6 files changedLine totals unavailable