chore(core): type checking for unit tests (#28529)

Issue number: N/A

---------

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issue. -->

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## What is the current behavior?
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Type checking inside of the Stencil unit tests have been disabled for a
long time. This has resulted in a difficult developer experience and
numerous issues (both types and implementation) within our unit tests.

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

- Type checking is now enabled for all Stencil unit tests
- Tests have been updated to resolve type errors and implementation
errors
- Many `as any` casts were introduced, as many legacy tests test invalid
configurations of functions that require it (for example passing
`undefined` to an argument that cannot be `undefined`).

## 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. -->

To test this PR you can checkout the branch locally. Install
dependencies in the `/core` directory to make sure you are on at least
`@stencil/core@4.7.2`.

Opening either a `.spec.ts` or `.spec.tsx` file, validate that your IDE
detects types and can provide auto completions for jest global types.

If you desire, you can provide an invalid type and try building the
project - you will observe the build will fail due to the invalid type.

core/src/components/segment/test/segment.spec.ts

@@ -9,14 +9,14 @@ it('should disable segment buttons added to disabled segment async', async () =>
     html: `<ion-segment disabled="true"></ion-segment>`,
   });
 
-  const segment = page.body.querySelector('ion-segment');
+  const segment = page.body.querySelector('ion-segment')!;
   segment.innerHTML = `
     <ion-segment-button>
       <ion-label>Segment Button</ion-label>
     </ion-segment-button>`;
   await page.waitForChanges();
 
-  const segmentButton = page.body.querySelector('ion-segment-button');
+  const segmentButton = page.body.querySelector('ion-segment-button')!;
   expect(segmentButton.disabled).toBe(true);
 });
 
@@ -32,7 +32,7 @@ it('should set checked state when value is set asynchronously', async () => {
     `,
   });
 
-  const segmentButton = page.root.querySelector('ion-segment-button');
+  const segmentButton = page.body.querySelector('ion-segment-button')!;
 
   expect(segmentButton.classList.contains('segment-button-checked')).toBe(false);