fix(react, vue): inline modals apply ion-page class (#27481)

Issue number: resolves #27470

---------

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## What is the current behavior?
<!-- Please describe the current behavior that you are modifying. -->

Passing multiple elements in to an inline modal causes `.ion-page` to
not get set. This causes content to get pushed off the bottom of the
modal equal to the height of the header. React has some special CSS that
prevents this:
eb2772c0ce/packages/react/src/components/createInlineOverlayComponent.tsx (L137-L140)

However, I think this should be delegated to `.ion-page` instead so the
behavior is consistent across frameworks. For example, Angular uses
`.ion-page`:
eb2772c0ce/angular/src/directives/overlays/modal.ts (L82)

## What is the new behavior?
<!-- Please describe the behavior or changes that are being added by
this PR. -->

- Inline overlays in Ionic React and Ionic Vue wrap child content in
`.ion-delegate-host.ion-page`.
- Removed the custom flex styles from Ionic React as `.ion-page` has its
own styles.

## Does this introduce a breaking change?

- [ ] Yes
- [x] No

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and migration path for existing applications below. -->


## Other information

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screenshots of how the component looks before and after the change. -->

Revised Design Doc:
https://github.com/ionic-team/ionic-framework-design-documents/pull/84

packages/vue/scripts/copy-overlays.js

@@ -25,7 +25,8 @@ function generateOverlays() {
     },
     {
       tag: 'ion-modal',
-      name: 'IonModal'
+      name: 'IonModal',
+      hasDelegateHost: true
     },
     {
       tag: 'ion-popover',
@@ -44,8 +45,10 @@ function generateOverlays() {
 
     componentImports.push(`import { defineCustomElement as ${defineCustomElementFn} } from '@ionic/core/components/${component.tag}.js'`);
 
+    const delegateHostString = component.hasDelegateHost ? ', true' : '';
+
     componentDefinitions.push(`
-export const ${component.name} = /*@__PURE__*/ defineOverlayContainer<JSX.${component.name}>('${component.tag}', ${defineCustomElementFn}, [${props.join(', ')}]);
+export const ${component.name} = /*@__PURE__*/ defineOverlayContainer<JSX.${component.name}>('${component.tag}', ${defineCustomElementFn}, [${props.join(', ')}]${delegateHostString});
     `);
   });