feat: Parallel Execution of Nodes in Workflows (#8192)

Co-authored-by: StyleZhang <jasonapring2015@outlook.com>
Co-authored-by: Yi <yxiaoisme@gmail.com>
Co-authored-by: -LAN- <laipz8200@outlook.com>

api/core/workflow/nodes/event.py

@@ -0,0 +1,20 @@
+from pydantic import BaseModel, Field
+
+from core.workflow.entities.node_entities import NodeRunResult
+
+
+class RunCompletedEvent(BaseModel):
+    run_result: NodeRunResult = Field(..., description="run result")
+
+
+class RunStreamChunkEvent(BaseModel):
+    chunk_content: str = Field(..., description="chunk content")
+    from_variable_selector: list[str] = Field(..., description="from variable selector")
+
+
+class RunRetrieverResourceEvent(BaseModel):
+    retriever_resources: list[dict] = Field(..., description="retriever resources")
+    context: str = Field(..., description="context")
+
+
+RunEvent = RunCompletedEvent | RunStreamChunkEvent | RunRetrieverResourceEvent