[Feature] Support return logprob of generated tokens (#2784)

* online chat support logprobs

* check xpu

* check vl_gpu_model_runner

* only cuda support logprob

* get_worker() check platform

---------

Co-authored-by: Jiang-Jia-Jun <163579578+Jiang-Jia-Jun@users.noreply.github.com>

fastdeploy/worker/worker_process.py

@@ -42,6 +42,8 @@ def get_worker(fd_config: FDConfig, local_rank: int, rank: int) -> WorkerBase:
     """
     get worker of different device
     """
+    if fd_config.model_config.enable_logprob and not current_platform.is_cuda():
+        raise NotImplementedError("Only CUDA platform supports logprob.")
     if current_platform.is_cuda():
         from fastdeploy.worker.gpu_worker import GpuWorker
         return GpuWorker(fd_config=fd_config, local_rank=local_rank, rank=rank)
@@ -550,6 +552,9 @@ def parse_args():
         "'ipc_snapshot': load from disk snapshot of IPC weights, "
         "'meta': provide RL traing worker, no_weights_load"
         "'normal':normal load weight")
+    parser.add_argument("--enable_logprob",
+                        action='store_true',
+                        help="Enable output of token-level log probabilities.")
 
     args = parser.parse_args()
     return args
@@ -771,6 +776,8 @@ def initialize_fd_config(config) -> FDConfig:
             "No quantization config found and use original weight and act dtype."
         )
 
+    model_config.enable_logprob = config.enable_logprob
+
     model_config.architectures = model_config_dict.get("architectures")
 
     # Update load config