Enable Async output process for HPU (#342)

FILL IN THE PR DESCRIPTION HERE

This PR refer to [vllm-project#7049](vllm-project#7049)
to implement Asynchronous Output Processor on HPU. It is open by
default, to disable it, please pass the `--disable_async_output_proc`
flag.

From my local test on latest habana_main branch(commit
29fb5ed), the throughput improves from
3847 TPS to 4011 TPS.

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DESCRIPTION ABOVE**

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</details>

vllm/config.py

@@ -372,9 +372,10 @@ def verify_async_output_proc(self, parallel_config, speculative_config,
             self.use_async_output_proc = False
             return
 
-        if device_config.device_type not in ("cuda", "tpu"):
+        if device_config.device_type not in ("cuda", "tpu", "hpu"):
             logger.warning(
-                "Async output processing is only supported for CUDA or TPU. "
+                "Async output processing is only supported for CUDA, TPU "
+                "and HPU. "
                 "Disabling it for other platforms.")
             self.use_async_output_proc = False
             return

vllm/worker/habana_model_runner.py

@@ -428,6 +428,7 @@ class ModelInputForHPU(ModelRunnerInputBase):
     virtual_engine: int = 0
     lora_mask: Optional[torch.Tensor] = None
     lora_logits_mask: Optional[torch.Tensor] = None
+    async_callback: Optional[Callable] = None
 
     def as_broadcastable_tensor_dict(self) -> Dict[str, Any]:
         tensor_dict = {
@@ -1934,6 +1935,9 @@ def execute_model(
         if not self.is_driver_worker:
             return []
 
+        if model_input.async_callback is not None:
+            model_input.async_callback()
+
         # Sample the next token.
         with self.profiler.record_event(
                 'internal', ('sample_'