refactor: Break apart monolithic configuration schema (#1977)

[skip ci]

src/config/schema/elements/custom/menu/icon.ts

@@ -0,0 +1,8 @@
+import { z } from 'zod';
+import { iconSchema } from '../../stock/icon';
+import { menuBaseSchema } from './base';
+
+export const menuIconSchema = menuBaseSchema.merge(iconSchema).extend({
+  type: z.literal('custom:advanced-camera-card-menu-icon'),
+});
+export type MenuIcon = z.infer<typeof menuIconSchema>;