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();
   }