[V1][Metrics] Add several request timing histograms (#12644)

Signed-off-by: Mark McLoughlin <markmc@redhat.com>

vllm/v1/engine/llm_engine.py

@@ -73,6 +73,7 @@ class LLMEngine:
             asyncio_mode=False,
             vllm_config=vllm_config,
             executor_class=executor_class,
+            log_stats=False,  # FIXME: implement
         )
 
     @classmethod