refactor(core): Improve test-webhooks (no-changelog) (#8069)

Remove duplication, improve readability, and expand tests for
`TestWebhooks.ts` - in anticipation for storing test webhooks in Redis.

---------

Co-authored-by: कारतोफ्फेलस्क्रिप्ट™ <aditya@netroy.in>

packages/core/src/NodeExecuteFunctions.ts

@@ -3768,7 +3768,6 @@ export function getExecuteHookFunctions(
 	additionalData: IWorkflowExecuteAdditionalData,
 	mode: WorkflowExecuteMode,
 	activation: WorkflowActivateMode,
-	isTest?: boolean,
 	webhookData?: IWebhookData,
 ): IHookFunctions {
 	return ((workflow: Workflow, node: INode) => {
@@ -3810,7 +3809,7 @@ export function getExecuteHookFunctions(
 					additionalData,
 					mode,
 					getAdditionalKeys(additionalData, mode, null),
-					isTest,
+					webhookData?.isTest,
 				);
 			},
 			getWebhookName(): string {