feat: (re-)enable Databricks inference adapter (#3500)

# What does this PR do?

add/enable the Databricks inference adapter

Databricks inference adapter was broken, closes #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 Plan

ci and 

```
./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

tests/integration/suites.py

@@ -108,6 +108,14 @@ SETUP_DEFINITIONS: dict[str, Setup] = {
             "embedding_model": "together/togethercomputer/m2-bert-80M-32k-retrieval",
         },
     ),
+    "databricks": Setup(
+        name="databricks",
+        description="Databricks models",
+        defaults={
+            "text_model": "databricks/databricks-meta-llama-3-3-70b-instruct",
+            "embedding_model": "databricks/databricks-bge-large-en",
+        },
+    ),
     "fireworks": Setup(
         name="fireworks",
         description="Fireworks provider with a text model",