chore: add new model configuration file for claude 3.7

What does this merge request do and why?

This merge request adds support for Claude 3.7 by introducing a new model configuration file. This allows us to integrate and evaluate the latest Claude model in our AI evaluation pipeline.

How to set up and validate locally

No prompt is using this model yet.

Merge request checklist

• Tests added for new functionality. If not, please raise an issue to follow up.
• Documentation added/updated, if needed.

Refers to gitlab-org/gitlab#521034

Closes https://gitlab.com/gitlab-org/gitlab/-/issues/521059

ai_gateway/prompts/model_configs/claude_3_7.yml

+name: claude-3-7-sonnet-20250219
+params:
+  temperature: 0.0
+  max_tokens: 4_096
+  max_retries: 1
+  model_class_provider: anthropic

[Nathan Weinshenker]

self-review: I went with naming the file claude_3_7.yml instead of a use case-based name, given our documentation doesn't fully describe the best naming conventions. We still don't know if this is the most performant model for our tools.