test(toast): reset config to avoid unnecessary setTimeouts (#29004)

Issue number: Internal

---------

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issue. -->

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

Team members are running into unexpected errors running spec tests:

```
TypeError: Cannot read properties of undefined (reading '$instanceValues$')
```

This line is the culprit:
https://github.com/ionic-team/ionic-framework/blob/f885a5526addab8abf93a95de8980e4ef78cbd36/core/src/components/toast/test/toast.spec.tsx#L108
We set the Ionic config for toastDuration to 5000. This means that on
present a setTimeout callback will fire after 5000ms and dismiss the
toast. For this test, this is fine because we never present the toast
therefore the setTimeout is never created.

The problem is that this config is not automatically reset between
tests. As a result, when we have tests that only present the toast (and
never dismiss it) the duration is also 5000 there:
https://github.com/ionic-team/ionic-framework/blob/f885a5526addab8abf93a95de8980e4ef78cbd36/core/src/components/toast/test/toast.spec.tsx#L179-L184

This results in a bunch of setTimeouts being created. The timeout
callback runs dismiss, and the body of that function tries to access
data on the host toast. Since the toast instance has already been torn
down (since the tests are done), the undefined error occurs.


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

- Reset the Ionic config after the test that sets `toastDuration` to
`5000`

## 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/toast/test/toast.spec.tsx

@@ -93,6 +93,19 @@ describe('toast: a11y smoke test', () => {
 });
 
 describe('toast: duration config', () => {
+  afterEach(() => {
+    /**
+     * Important: Reset the config
+     * after each test as it is not
+     * automatically reset.
+     * Otherwise, toasts in other tests
+     * will take on any toastDuration value
+     * set and timeouts will potentially run
+     * after tests are finished.
+     */
+    config.reset({});
+  });
+
   it('should have duration set to 0', async () => {
     const page = await newSpecPage({
       components: [Toast],