fix(input, searchbar, textarea): ensure nativeInput is always available (#28362)

Issue number: resolves #28283 

---------

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issue. -->

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

`getInputElement()` is used to access the native input. If the component
has yet to render, then the function will return `undefined`. This
happens mostly when using `ref` on React.

```tsx
<IonInput ref={async input => {
  const nativeInput = await input.getInputElement();
  // nativeInput is undefined
}} />
```

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

- `getInputElement()` will wait to return once the component is ready.

## Does this introduce a breaking change?

- [ ] Yes
- [x] No

<!-- If this introduces a breaking change, please describe the impact
and migration path for existing applications below. -->


## Other information

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

Dev build: `7.5.1-dev.11697488622.175c9183`

core/src/components/textarea/textarea.tsx

@@ -16,7 +16,13 @@ import {
 import type { LegacyFormController, NotchController } from '@utils/forms';
 import { createLegacyFormController, createNotchController } from '@utils/forms';
 import type { Attributes } from '@utils/helpers';
-import { inheritAriaAttributes, debounceEvent, findItemLabel, inheritAttributes } from '@utils/helpers';
+import {
+  inheritAriaAttributes,
+  debounceEvent,
+  findItemLabel,
+  inheritAttributes,
+  componentOnReady,
+} from '@utils/helpers';
 import { printIonWarning } from '@utils/logging';
 import { createSlotMutationController } from '@utils/slot-mutation-controller';
 import type { SlotMutationController } from '@utils/slot-mutation-controller';
@@ -378,7 +384,14 @@ export class Textarea implements ComponentInterface {
    * Returns the native `<textarea>` element used under the hood.
    */
   @Method()
-  getInputElement(): Promise<HTMLTextAreaElement> {
+  async getInputElement(): Promise<HTMLTextAreaElement> {
+    /**
+     * If this gets called in certain early lifecycle hooks (ex: Vue onMounted),
+     * nativeInput won't be defined yet with the custom elements build, so wait for it to load in.
+     */
+    if (!this.nativeInput) {
+      await new Promise((resolve) => componentOnReady(this.el, resolve));
+    }
     return Promise.resolve(this.nativeInput!);
   }