[Bug]: MvxSpinner not appearing in fragments
### Description

I'm upgrading a Xamarin Android app that used MvvmCross v8.0.2 to .NET 8 for Android with MvvmCross v9.2.0 and having a problem with our MvxSpinners not appearing. Our Fragments and Activities have not changed and nor have the ViewModel properties bound to the spinners.

One thing that has changed is the base theme from `Theme.AppCompat.Light.NoActionBar` to `Theme.MaterialComponents.Light.NoActionBar.Bridge`. This was done to prevent Syncfusion controls crashing the app when they try to show an error message using a Material themed dialog - something we have no control over.

Simplified version of one of our fragments, neither spinner is shown in the latest version:

```xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:local="http://schemas.android.com/apk/res-auto"
    android:orientation="vertical"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:background="@color/white">
    <include
        layout="@layout/toolbar_actionbar" />
    <RelativeLayout
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:padding="10dp">
        <TextView
            style="@style/TextViewPrimaryText"
            android:text="Navigation Service"
            android:id="@+id/tv_navservice"
            android:layout_centerInParent="true"
            android:layout_alignParentLeft="true"
            android:paddingBottom="2dp"
            android:paddingTop="2dp" />
        <mvvmcross.platforms.android.binding.views.MvxSpinner
            android:id="@+id/sp_navservice"
            android:background="@color/button"
            android:layout_centerInParent="true"
            android:layout_alignParentRight="true"
            android:layout_width="150dp"
            android:gravity="right"
            android:layout_gravity="right"
            android:layout_height="wrap_content"
            android:layout_marginRight="4dp"
            local:MvxItemTemplate="@layout/item_spinner"
            local:MvxDropDownItemTemplate="@android:layout/simple_spinner_dropdown_item"
            local:MvxBind="ItemsSource NavigationChoices; SelectedItem NavigationChoice;"
            />
    </RelativeLayout>
    <View
        android:layout_width="match_parent"
        android:layout_height="1dp"
        android:background="@color/light_gray" />
    <RelativeLayout
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:padding="10dp">
        <TextView
            style="@style/TextViewPrimaryText"
            android:text="Email Log Files"
            android:id="@+id/tv_email"
            android:layout_centerInParent="true"
            android:layout_alignParentLeft="true"
            android:paddingBottom="2dp"
            android:paddingTop="2dp" />
        <Button
            style="@style/ButtonStyle"
            android:id="@+id/button_email"
            android:text="Email"
            android:layout_centerInParent="true"
            android:layout_alignParentRight="true"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content" />
    </RelativeLayout>
    <View
        android:layout_width="match_parent"
        android:layout_height="1dp"
        android:background="@color/light_gray" />
    <RelativeLayout
        android:layout_width="fill_parent"
        android:layout_height="wrap_content"
        android:padding="10dp">
        <TextView
            style="@style/TextViewPrimaryText"
            android:text="Automatically display keyboard with numeric Task Entry popup"
            android:id="@+id/tv_numkeys"
            android:layout_centerInParent="true"
            android:layout_alignParentLeft="true"
            android:paddingBottom="2dp"
            android:paddingTop="2dp"
            android:paddingRight="80dp"
            android:singleLine="false"
            />
        <mvvmcross.platforms.android.binding.views.MvxSpinner
            android:id="@+id/sp_numkeys"
            android:background="@color/button"
            android:layout_centerInParent="true"
            android:layout_alignParentRight="true"
            android:layout_width="70dp"
            android:gravity="right"
            android:layout_gravity="right"
            android:layout_height="wrap_content"
            android:layout_marginRight="4dp"
            local:MvxItemTemplate="@layout/item_spinner"
            local:MvxDropDownItemTemplate="@android:layout/simple_spinner_dropdown_item"
            local:MvxBind="ItemsSource ShowKeyboardChoices; SelectedItem ShowKeyboardChoice;"
            />
    </RelativeLayout>
</LinearLayout>
```

I have tried removing the style templates to see if that made a difference, it did not. I also tried fully qualifying the MvxSpinner although we did not need that previously but it did not help.

Is MvxSpinner compatible with a Material theme?

Are there any new requirements for MvxSpinner in MvvmCross v9.0.2 or .NET for Android?


### Steps to Reproduce

1. Update a Xamarin Android app that includes MvxSpinners to .NET 8 for Android.
2. Run the app.
3. MvxSpinners do not appear.

### Link to public reproduction project repository

_No response_

### Version with bug

9.2.0

### Is this a regression from previous behavior?

Yes, this used to work in a previous version

### Last version that worked well

8.0.0

### Affected platforms

Android

### Affected platform versions

34

### Did you find any workaround?

_No response_