feat(verification): various improvements (#1921)

# What does this PR do?
- provider and their models now live in config.yaml
- better distinguish different cases within a test
- add model key to surface provider's model_id
- include example command to rerun single test case

## Test Plan
<img width="1173" alt="image"
src="https://github.com/user-attachments/assets/b414baf0-c768-451f-8c3b-c2905cf36fac"
/>

tests/verifications/conf/cerebras.yaml

@@ -0,0 +1,10 @@
+base_url: https://api.cerebras.ai/v1
+api_key_var: CEREBRAS_API_KEY
+models:
+- llama-3.3-70b
+model_display_names:
+  llama-3.3-70b: Llama-3.3-70B-Instruct
+test_exclusions:
+  llama-3.3-70b:
+  - test_chat_non_streaming_image
+  - test_chat_streaming_image