feat: add llm blocking invoke (#15732)

api/core/plugin/backwards_invocation/model.py

 from collections.abc import Generator
 
 from core.model_manager import ModelManager
-from core.model_runtime.entities.llm_entities import LLMResult, LLMResultChunk
+from core.model_runtime.entities.llm_entities import LLMResult, LLMResultChunk, LLMResultChunkDelta
 from core.model_runtime.entities.message_entities import (
     PromptMessage,
     SystemPromptMessage,
             model_parameters=payload.completion_params,
             tools=payload.tools,
             stop=payload.stop,
-            stream=payload.stream or True,
+            stream=True if payload.stream is None else payload.stream,
             user=user_id,
         )
 
         else:
             if response.usage:
                 LLMNode.deduct_llm_quota(tenant_id=tenant.id, model_instance=model_instance, usage=response.usage)
-            return response
+
+            def handle_non_streaming(response: LLMResult) -> Generator[LLMResultChunk, None, None]:
+                yield LLMResultChunk(
+                    model=response.model,
+                    prompt_messages=response.prompt_messages,
+                    system_fingerprint=response.system_fingerprint,
+                    delta=LLMResultChunkDelta(
+                        index=0,
+                        message=response.message,
+                        usage=response.usage,
+                        finish_reason="",
+                    ),
+                )
+
+            return handle_non_streaming(response)
 
     @classmethod
     def invoke_text_embedding(cls, user_id: str, tenant: Tenant, payload: RequestInvokeTextEmbedding):