Implement a CustomCombo node (#7142)

Adds a frontend support for a "Custom Combo" node which contains a Combo
Widget, and a growing list of string inputs that determine the options
available to the combo.

![Custom
Combo](https://github.com/user-attachments/assets/3b5a1f68-ce2f-47f1-9ae4-dbb99f610d84)

By promoting the combo widget on this node, a list of options determined
by workflow builders can be exposed to end users.

CC: @Kosinkadink

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-7142-Implement-a-CustomCombo-node-2bf6d73d36508161951df01009a7262f)
by [Unito](https://www.unito.io)

src/extensions/core/index.ts

@@ -2,6 +2,7 @@ import { isCloud } from '@/platform/distribution/types'
 
 import './clipspace'
 import './contextMenuFilter'
+import './customCombo'
 import './dynamicPrompts'
 import './editAttention'
 import './electronAdapter'