feat(core): Add support for building LLM applications (#7235)

This extracts all core and editor changes from #7246 and #7137, so that
we can get these changes merged first.

ADO-1120

[DB Tests](https://github.com/n8n-io/n8n/actions/runs/6379749011)
[E2E Tests](https://github.com/n8n-io/n8n/actions/runs/6379751480)
[Workflow Tests](https://github.com/n8n-io/n8n/actions/runs/6379752828)

---------

Co-authored-by: Jan Oberhauser <jan.oberhauser@gmail.com>
Co-authored-by: Oleg Ivaniv <me@olegivaniv.com>
Co-authored-by: Alex Grozav <alex@grozav.com>
Co-authored-by: कारतोफ्फेलस्क्रिप्ट™ <aditya@netroy.in>

packages/editor-ui/src/components/NodeSettings.vue

@@ -168,7 +168,7 @@ import type {
 	INodeProperties,
 	NodeParameterValue,
 } from 'n8n-workflow';
-import { NodeHelpers, deepCopy } from 'n8n-workflow';
+import { NodeHelpers, NodeConnectionType, deepCopy } from 'n8n-workflow';
 import type {
 	INodeUi,
 	INodeUpdatePropertiesInformation,
@@ -233,6 +233,13 @@ export default defineComponent({
 			return this.readOnly || this.hasForeignCredential;
 		},
 		isExecutable(): boolean {
+			if (
+				this.nodeType &&
+				!this.isTriggerNode &&
+				!this.nodeType.inputs.includes(NodeConnectionType.Main)
+			) {
+				return false;
+			}
 			return this.executable || this.hasForeignCredential;
 		},
 		nodeTypeName(): string {