feat: (re-)enable Databricks inference adapter

Databricks inference adapter was broken, would not start, see #3486

- remove deprecated completion / chat_completion endpoints
- enable dynamic model listing w/o refresh, listing is not async
- use SecretStr instead of str for token
- backward incompatible change: for consistency with databricks docs, env DATABRICKS_URL -> DATABRICKS_HOST and DATABRICKS_API_TOKEN -> DATABRICKS_TOKEN
- databricks urls are custom per user/org, add special recorder handling for databricks urls
- add integration test --setup databricks
- enable chat completions tests
- enable embeddings tests
- disable n > 1 tests
- disable embeddings base64 tests
- disable embeddings dimensions tests

note: reasoning models, e.g. gpt oss, fail because databricks has a custom, incompatible response format

test with: ./scripts/integration-tests.sh --stack-config server:ci-tests --setup databricks --subdirs inference --pattern openai

note: databricks needs to be manually added to the ci-tests distro for replay testing

llama_stack/testing/inference_recorder.py

@@ -262,6 +262,10 @@ async def _patched_inference_method(original_method, self, client_type, endpoint
         raise ValueError(f"Unknown client type: {client_type}")
 
     url = base_url.rstrip("/") + endpoint
+    # Special handling for Databricks URLs to avoid leaking workspace info
+    # e.g. https://adb-1234567890123456.7.cloud.databricks.com -> https://...cloud.databricks.com
+    if "cloud.databricks.com" in url:
+        url = "__databricks__" + url.split("cloud.databricks.com")[-1]
     method = "POST"
     headers = {}
     body = kwargs