feat: add refresh_models support to inference adapters (default: false) (#3719)

# What does this PR do?

inference adapters can now configure `refresh_models: bool` to control
periodic model listing from their providers

BREAKING CHANGE: together inference adapter default changed. previously
always refreshed, now follows config.

addresses "models: refresh" on #3517

## Test Plan

ci w/ new tests

llama_stack/providers/remote/inference/databricks/databricks.py

@@ -41,9 +41,6 @@ class DatabricksInferenceAdapter(OpenAIMixin):
             ).serving_endpoints.list()  # TODO: this is not async
         ]
 
-    async def should_refresh_models(self) -> bool:
-        return False
-
     async def openai_completion(
         self,
         model: str,