fix(menu): refs are not destroyed on unmount (#27141)

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## What is the current behavior?
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Issue URL: resolves
#24907

`ion-menu` currently clears the `menuInnerEl` and `backdropEl` refs
created by Stencil when `disconnectedCallback` is fired. If the
`ion-menu` component is re-mounted but _not_ re-rendered, those refs
will still be `undefined` when the `open` method is called, resulting in
the linked issue. Note that if the `ion-menu` re-renders before `open`
is called then this issue does not reproduce.

This clearing behavior was added ~6 years ago before we utilized Stencil
refs:
https://github.com/ionic-team/ionic-framework/blob/687b37ad3e3237b874473817bb7b59143ac113ce/packages/core/src/components/menu/menu.tsx#L136-L137

During this time we had to manually create and clear the element
references.

Several years later we moved to using Stencil refs, but we did not
remove the logic that clears the refs:
d83d8ee

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

- Menu no longer sets `menuInnerEl` and `backdropEl` to `undefined` in
`disconnectedCallback`.
- The `close` method is called so that the state is reset prior to the
menu being re-added. I observed that without this, the animation to
re-present a menu did not work correctly.

## 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/menu/menu.tsx

@@ -241,7 +241,16 @@ export class Menu implements ComponentInterface, MenuI {
     this.updateState();
   }
 
-  disconnectedCallback() {
+  async disconnectedCallback() {
+    /**
+     * The menu should be closed when it is
+     * unmounted from the DOM.
+     * This is an async call, so we need to wait for
+     * this to finish otherwise contentEl
+     * will not have MENU_CONTENT_OPEN removed.
+     */
+    await this.close(false);
+
     this.blocker.destroy();
     menuController._unregister(this);
     if (this.animation) {
@@ -253,7 +262,7 @@ export class Menu implements ComponentInterface, MenuI {
     }
 
     this.animation = undefined;
-    this.contentEl = this.backdropEl = this.menuInnerEl = undefined;
+    this.contentEl = undefined;
   }
 
   @Listen('ionSplitPaneVisible', { target: 'body' })