fix(datetime-button): log error if non-datetime instance is passed (#27456)

Issue number: N/A

---------

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issue. -->

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## What is the current behavior?
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An issue was filed in
https://github.com/ionic-team/ionic-framework/issues/27452 where the
`presentation` property was not being respected. The problem ended up
being that the ID passed to `ion-datetime-button` was not associated
with an `ion-datetime` instance, so it did not pick up on the
`presentation` property. I think we can handle this better by logging an
error if the ID passed does not belong to an `ion-datetime`.

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

- Log an error if the ID passed to `ion-datetime-button` exists but does
not belong to an `ion-datetime` instance.

## 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. -->

core/src/components/datetime-button/datetime-button.tsx

@@ -75,6 +75,18 @@ export class DatetimeButton implements ComponentInterface {
       return;
     }
 
+    /**
+     * The element reference must be an ion-datetime. Print an error
+     * if a non-datetime element was provided.
+     */
+    if (datetimeEl.tagName !== 'ION-DATETIME') {
+      printIonError(
+        `Expected an ion-datetime instance for ID '${datetime}' but received '${datetimeEl.tagName.toLowerCase()}' instead.`,
+        datetimeEl
+      );
+      return;
+    }
+
     /**
      * Since the datetime can be used in any context (overlays, accordion, etc)
      * we track when it is visible to determine when it is active.