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/providers/remote/inference/databricks/config.py

@@ -6,7 +6,7 @@
 
 from typing import Any
 
-from pydantic import BaseModel, Field
+from pydantic import BaseModel, Field, SecretStr
 
 from llama_stack.schema_utils import json_schema_type
 
@@ -17,16 +17,16 @@ class DatabricksImplConfig(BaseModel):
         default=None,
         description="The URL for the Databricks model serving endpoint",
     )
-    api_token: str = Field(
-        default=None,
+    api_token: SecretStr = Field(
+        default=SecretStr(None),
         description="The Databricks API token",
     )
 
     @classmethod
     def sample_run_config(
         cls,
-        url: str = "${env.DATABRICKS_URL:=}",
-        api_token: str = "${env.DATABRICKS_API_TOKEN:=}",
+        url: str = "${env.DATABRICKS_HOST:=}",
+        api_token: str = "${env.DATABRICKS_TOKEN:=}",
         **kwargs: Any,
     ) -> dict[str, Any]:
         return {