fix(overlays): focus management with checkbox/radio (#30026)

Issue number: resolves internal

---------

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

Using `Tab` or `Shift + Tab` to focus through elements in a modal won't
behave as expected when using `ion-checkbox` or `ion-radio` within an
`ion-item`. Previously, the behavior would result in the last item in a
list getting focus styling, but `document.activeElement` would still be
the first actionable item in the overlay

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

For checkboxes, the `ion-checkbox` element itself will be focused rather
than the encapsulating `ion-item`

For radios, the `ion-radio-group` will be used to focus the appropriate
element. This will be the first `ion-radio` if there is no "checked"
item, or the "checked" item if one exists.

## Does this introduce a breaking change?

- [ ] Yes
- [x] No

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## Other information

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

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

@@ -1,5 +1,5 @@
 import type { ComponentInterface, EventEmitter } from '@stencil/core';
-import { Component, Element, Event, Host, Listen, Prop, Watch, h } from '@stencil/core';
+import { Component, Element, Event, Host, Listen, Method, Prop, Watch, h } from '@stencil/core';
 import { renderHiddenInput } from '@utils/helpers';
 
 import { getIonMode } from '../../global/ionic-global';
@@ -217,6 +217,13 @@ export class RadioGroup implements ComponentInterface {
     }
   }
 
+  /** @internal */
+  @Method()
+  async setFocus() {
+    const radioToFocus = this.getRadios().find((r) => r.tabIndex !== -1);
+    radioToFocus?.setFocus();
+  }
+
   render() {
     const { label, labelId, el, name, value } = this;
     const mode = getIonMode(this);