support theme icons in menus in the shadow dom

Can we remove the two lines at https://github.com/microsoft/vscode/blob/68976705968229accd11fdfe1cba36a908208dc9/src/vs/base/browser/ui/menu/menu.ts#L1030 There rules are already dynamically created in the platform theme service (https://github.com/microsoft/vscode/blob/main/src/vs/platform/theme/browser/iconsStyleSheet.ts) They are using the configured product icon theme which could replace all icons, including the menu icons.