src/vs/platform/actions/common/actions.ts/SubmenuItemAction/actions
class SubmenuItemAction:	override get actions(): readonly IAction[] {
		const result: IAction[] = [];
		const menu = this._menuService.createMenu(this.item.submenu, this._contextKeyService);
		const groups = menu.getActions(this._options);
		menu.dispose();
		for (const [, actions] of groups) {
			if (actions.length > 0) {
				result.push(...actions);
				result.push(new Separator());
			}
		}
		if (result.length) {
			result.pop(); // remove last separator
		}
		return result;
	}