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/split-pane/split-pane.tsx

@@ -1,7 +1,6 @@
 import { Component, ComponentInterface, Element, Event, EventEmitter, Prop, State, Watch } from '@stencil/core';
 
 import { Mode } from '../../interface';
-import { createThemedClasses } from '../../utils/theme';
 
 const SPLIT_PANE_MAIN = 'split-pane-main';
 const SPLIT_PANE_SIDE = 'split-pane-side';
@@ -165,7 +164,11 @@ export class SplitPane implements ComponentInterface {
   hostData() {
     return {
       class: {
-        ...createThemedClasses(this.mode, 'split-pane'),
+        [`${this.mode}`]: true,
+
+        // Used internally for styling
+        [`split-pane-${this.mode}`]: true,
+
         'split-pane-visible': this.visible
       }
     };