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/recordings/responses/29585e055e6f.json

@@ -0,0 +1,56 @@
+{
+  "request": {
+    "method": "POST",
+    "url": "__databricks__/serving-endpoints/v1/chat/completions",
+    "headers": {},
+    "body": {
+      "model": "databricks-meta-llama-3-3-70b-instruct",
+      "messages": [
+        {
+          "role": "user",
+          "content": "Which planet has rings around it with a name starting with letter S?"
+        }
+      ],
+      "stream": false
+    },
+    "endpoint": "/v1/chat/completions",
+    "model": "databricks-meta-llama-3-3-70b-instruct"
+  },
+  "response": {
+    "body": {
+      "__type__": "openai.types.chat.chat_completion.ChatCompletion",
+      "__data__": {
+        "id": "chatcmpl_094a74d8-2e39-45ce-8eb9-64d505bd24e9",
+        "choices": [
+          {
+            "finish_reason": "stop",
+            "index": 0,
+            "logprobs": null,
+            "message": {
+              "content": "The answer is Saturn! Saturn is a planet in our solar system that is known for its stunning ring system. The rings of Saturn are made up of ice and rock particles that range in size from tiny dust grains to massive boulders. They are a beautiful sight to behold, and astronomers and space enthusiasts alike have been fascinated by them for centuries.\n\nSo, the planet with rings around it with a name starting with the letter S is indeed Saturn!",
+              "refusal": null,
+              "role": "assistant",
+              "annotations": null,
+              "audio": null,
+              "function_call": null,
+              "tool_calls": null
+            }
+          }
+        ],
+        "created": 1758326504,
+        "model": "meta-llama-3.3-70b-instruct-121024",
+        "object": "chat.completion",
+        "service_tier": null,
+        "system_fingerprint": null,
+        "usage": {
+          "completion_tokens": 91,
+          "prompt_tokens": 24,
+          "total_tokens": 115,
+          "completion_tokens_details": null,
+          "prompt_tokens_details": null
+        }
+      }
+    },
+    "is_streaming": false
+  }
+}