Ensure that run managers are returned from handleLLMStart/handleChatM…

…odelStart always in the same order as the prompts passed in

What was happening was that the runManager was only added to the managers array after the callback handlers finished executing, so eg if the callback handlers for the second run finished first the runManager for prompt #2 would actually be in position #1 of the returned array.

langchain/src/callbacks/manager.ts

@@ -348,9 +348,7 @@ export class CallbackManager
     _parentRunId: string | undefined = undefined,
     extraParams: Record<string, unknown> | undefined = undefined
   ): Promise<CallbackManagerForLLMRun[]> {
-    const managers: CallbackManagerForLLMRun[] = [];
-
-    await Promise.all(
+    return Promise.all(
       prompts.map(async (prompt) => {
         const runId = uuidv4();
 
@@ -377,20 +375,16 @@ export class CallbackManager
           )
         );
 
-        managers.push(
-          new CallbackManagerForLLMRun(
-            runId,
-            this.handlers,
-            this.inheritableHandlers,
-            this.tags,
-            this.inheritableTags,
-            this._parentRunId
-          )
+        return new CallbackManagerForLLMRun(
+          runId,
+          this.handlers,
+          this.inheritableHandlers,
+          this.tags,
+          this.inheritableTags,
+          this._parentRunId
         );
       })
     );
-
-    return managers;
   }
 
   async handleChatModelStart(
@@ -400,9 +394,7 @@ export class CallbackManager
     _parentRunId: string | undefined = undefined,
     extraParams: Record<string, unknown> | undefined = undefined
   ): Promise<CallbackManagerForLLMRun[]> {
-    const managers: CallbackManagerForLLMRun[] = [];
-
-    await Promise.all(
+    return Promise.all(
       messages.map(async (messageGroup) => {
         const runId = uuidv4();
 
@@ -441,20 +433,16 @@ export class CallbackManager
           )
         );
 
-        managers.push(
-          new CallbackManagerForLLMRun(
-            runId,
-            this.handlers,
-            this.inheritableHandlers,
-            this.tags,
-            this.inheritableTags,
-            this._parentRunId
-          )
+        return new CallbackManagerForLLMRun(
+          runId,
+          this.handlers,
+          this.inheritableHandlers,
+          this.tags,
+          this.inheritableTags,
+          this._parentRunId
         );
       })
     );
-
-    return managers;
   }
 
   async handleChainStart(