[v1] Refactor KVCacheConfig (#14079)

Signed-off-by: Chen Zhang <zhangch99@outlook.com>

vllm/v1/worker/worker_base.py

@@ -51,7 +51,7 @@ class WorkerBase(WorkerBaseV0):
         self.device: Optional[torch.device] = None
         self.model_runner: Optional[nn.Module] = None
 
-    def get_kv_cache_spec(self) -> KVCacheSpec:
+    def get_kv_cache_spec(self) -> dict[str, KVCacheSpec]:
         """Get specifications for KV cache implementation."""
         raise NotImplementedError