Add overlap scheduling for embeddings code path (#14032)

Co-authored-by: Satyam Kumar <satyamk@linkedin.com>

python/sglang/srt/managers/scheduler_output_processor_mixin.py

@@ -224,6 +224,9 @@ class SchedulerOutputProcessorMixin:
                     )
 
         else:  # embedding or reward model
+            if result.copy_done is not None:
+                result.copy_done.synchronize()
+
             is_sparse = envs.SGLANG_EMBEDDINGS_SPARSE_HEAD.is_set()
 
             embeddings = result.embeddings