fix(alert): do not overwrite id set in htmlAttributes (#29708)

Issue number: resolves #29704

---------

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## What is the current behavior?
Setting the id of an alert via htmlAttributes doesn't work due to it
being overwritten by the overlay id.

## What is the new behavior?
Setting the id of an alert via htmlAttributes works.

## Does this introduce a breaking change?

- [ ] Yes
- [x] No

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## Other information

First time PR, long time fan. Please let me know if I missed any of the
contributing guidelines, happy to change anything!

core/src/components/alert/alert.tsx

@@ -341,7 +341,9 @@ export class Alert implements ComponentInterface, OverlayInterface {
   }
 
   componentWillLoad() {
-    setOverlayId(this.el);
+    if (!this.htmlAttributes?.id) {
+      setOverlayId(this.el);
+    }
     this.inputsChanged();
     this.buttonsChanged();
   }

core/src/components/alert/test/alert.spec.ts → core/src/components/alert/test/alert.spec.tsx

@@ -2,6 +2,7 @@ import { newSpecPage } from '@stencil/core/testing';
 
 import { config } from '../../../global/config';
 import { Alert } from '../alert';
+import { h } from '@stencil/core';
 
 describe('alert: custom html', () => {
   it('should not allow for custom html by default', async () => {
@@ -38,4 +39,15 @@ describe('alert: custom html', () => {
     expect(content.textContent).toContain('Custom Text');
     expect(content.querySelector('button.custom-html')).toBe(null);
   });
+
+  it('should not overwrite the id set in htmlAttributes', async () => {
+    const id = 'custom-id';
+    const page = await newSpecPage({
+      components: [Alert],
+      template: () => <ion-alert htmlAttributes={{ id }} overlayIndex={-1}></ion-alert>,
+    });
+
+    const alert = page.body.querySelector('ion-alert')!;
+    expect(alert.id).toBe(id);
+  });
 });