GH-36493
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Validate extension JSON: Error: Field 'classes/PopupMenu/methods/add_icon_shortcut/arguments': size changed value in new API, from 4 to 5.
Validate extension JSON: Error: Field 'classes/PopupMenu/methods/add_shortcut/arguments': size changed value in new API, from 3 to 4.

Added optional argument. Compatibility methods registered.
