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/inference/test_openai_completion.py

@@ -98,6 +98,7 @@ def skip_if_doesnt_support_n(client_with_models, model_id):
         #  the entered value was 2. Update the candidateCount value and try again.', 'status': 'INVALID_ARGUMENT'}
         "remote::tgi",  # TGI ignores n param silently
         "remote::together",  # `n` > 1 is not supported when streaming tokens. Please disable `stream`
+        "remote::databricks",  # Bad request: parameter "n" must be equal to 1 for streaming mode
     ):
         pytest.skip(f"Model {model_id} hosted by {provider.provider_type} doesn't support n param.")
 
@@ -110,7 +111,6 @@ def skip_if_model_doesnt_support_openai_chat_completion(client_with_models, mode
         "inline::vllm",
         "remote::bedrock",
         "remote::cerebras",
-        "remote::databricks",
         "remote::runpod",
         "remote::watsonx",  # watsonx returns 404 when hitting the /openai/v1 endpoint
     ):