feat(core): Add optional Error-Output (#7460)

Add an additional optional error output to which all items get sent that
could not be processed.
![Screenshot from 2023-10-18
17-29-15](https://github.com/n8n-io/n8n/assets/6249596/e9732807-ab2b-4662-a5f6-bdff24f7ad55)

Github issue / Community forum post (link here to close automatically):
https://community.n8n.io/t/error-connector-for-nodes/3094

https://community.n8n.io/t/error-handling-at-node-level-detect-node-execution-status/26791

---------

Co-authored-by: OlegIvaniv <me@olegivaniv.com>

packages/workflow/src/RoutingNode.ts

@@ -121,8 +121,9 @@ export class RoutingNode {
 
 		// TODO: Think about how batching could be handled for REST APIs which support it
 		for (let i = 0; i < items.length; i++) {
+			let thisArgs: IExecuteSingleFunctions | undefined;
 			try {
-				const thisArgs = nodeExecuteFunctions.getExecuteSingleFunctions(
+				thisArgs = nodeExecuteFunctions.getExecuteSingleFunctions(
 					this.workflow,
 					this.runExecutionData,
 					runIndex,
@@ -209,7 +210,7 @@ export class RoutingNode {
 
 				returnData.push(...responseData);
 			} catch (error) {
-				if (get(this.node, 'continueOnFail', false)) {
+				if (thisArgs !== undefined && thisArgs.continueOnFail()) {
 					returnData.push({ json: {}, error: error.message });
 					continue;
 				}