[KVConnector][Feature] Support KV connector cache reset via /reset_prefix_cache (#27170)

Signed-off-by: tovam <tovam@pliops.com>
Signed-off-by: Tova Movshovitz <tovam@pliops.com>
Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

vllm/engine/protocol.py

@@ -116,8 +116,10 @@ class EngineClient(ABC):
         ...
 
     @abstractmethod
-    async def reset_prefix_cache(self, reset_running_requests: bool = False) -> bool:
-        """Reset the prefix cache"""
+    async def reset_prefix_cache(
+        self, reset_running_requests: bool = False, reset_connector: bool = False
+    ) -> bool:
+        """Reset the prefix cache and optionally any configured connector cache"""
         ...
 
     @abstractmethod