fix(components): include mode classes on components for use in shadow (#17838)

- removes mode-less component classes from the internal CSS, use element instead
- adds mode specific classes `md` or `ios` for styling inside of shadow components
- adds e2e test that verifies mode classes exist on all ionic components, plus checks for specific classes that the components need for internal styling

fixes #17608

core/src/components/item-group/item-group.tsx

@@ -1,7 +1,6 @@
 import { Component, ComponentInterface } from '@stencil/core';
 
 import { Mode } from '../../interface';
-import { createThemedClasses } from '../../utils/theme';
 
 @Component({
   tag: 'ion-item-group',
@@ -18,8 +17,12 @@ export class ItemGroup implements ComponentInterface {
     return {
       'role': 'group',
       class: {
-        ...createThemedClasses(this.mode, 'item-group'),
-        'item': true,
+        [`${this.mode}`]: true,
+
+        // Used internally for styling
+        [`item-group-${this.mode}`]: true,
+
+        'item': true
       }
     };
   }