Android ListenableWorker MvxSetupSingleton.EnsureInitialized() crashes with InvalidOperationException
## 🐛 Bug Report

When trying to initialize MvvmCross from a background worker when the main application is not open, calling `MvvmCross.Core.MvxSetupSingleton.EnsureInitialized()` crashes the app with `System.InvalidOperationException: Cannot create Views Container without ApplicationContext` due to `public Context? ApplicationContext => _currentTopActivity?.Activity?.ApplicationContext;` being null in `MvvmCross.Platforms.Android.Core.MvxAndroidSetup`

```
MvvmCross.Platforms.Android.Core.MvxAndroidSetup.CreateViewsContainer(IMvxIoCProvider iocProvider)
MvvmCross.Core.MvxSetup.InitializeViewsContainer(IMvxIoCProvider iocProvider)
MvvmCross.Core.MvxSetup.InitializeSecondary()
MvvmCross.Core.MvxSetupSingleton.<StartSetupInitialization>b__13_0()
MvvmCross.Core.MvxSetupSingleton.EnsureInitialized()
Judah.NightOut.Droid.Workers.WorkerBase`1[[Judah.Client.CoreStandard.Messages.DeleteLocalMediaMessageCacheEntry, Judah.Client.CoreStandard, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]].Initialize()
Judah.NightOut.Droid.Workers.WorkerBase`1[[Judah.Client.CoreStandard.Messages.DeleteLocalMediaMessageCacheEntry, Judah.Client.CoreStandard, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]]..ctor(Context context, WorkerParameters workerParams)
Judah.NightOut.Droid.Workers.DeleteLocalMediaCacheWorker..ctor(Context context, WorkerParameters workerParams)
System.Reflection.ConstructorInvoker.InterpretedInvoke(Object obj, Span`1 args, BindingFlags invokeAttr)
```

### Expected behavior
MvvmCross should initialize without a current top activity

### Reproduction steps
Create a periodic work request in MainApplication that will run after the app is closed


```
public class MainApplication : MvxAndroidApplication<Setup, App>
{
    public MainApplication(IntPtr javaReference, JniHandleOwnership transfer)
        : base(javaReference, transfer)
    {
    }

    public override void OnCreate()
    {
        base.OnCreate();

        var constraintsBuilder = new Constraints.Builder();
        constraintsBuilder.SetRequiredNetworkType(NetworkType.NotRequired);
        var constraints = constraintsBuilder.Build();
        var workRequest = new PeriodicWorkRequest.Builder(typeof(DummyWorker), new TimeSpan(0, 1, 0))
            .SetConstraints(constraints)
            .Build();
        WorkManager.GetInstance(ApplicationContext).EnqueueUniquePeriodicWork(nameof(DummyWorker), ExistingPeriodicWorkPolicy.Replace, workRequest);
    }
}
```

```
public class DummyWorker : ListenableWorker, CallbackToFutureAdapter.IResolver
{
    public DummyWorker(IntPtr javaReference, JniHandleOwnership transfer) : base(javaReference, transfer)
    {
        Initialize();
    }

    protected DummyWorker(Context context, WorkerParameters workerParams) : base(context, workerParams)
    {
        Initialize();
    }

    private void Initialize()
    {
        var setup = MvxAndroidSetupSingleton.EnsureSingletonAvailable(ApplicationContext);
        setup.EnsureInitialized();
    }

    public override IListenableFuture StartWork()
    {
        return CallbackToFutureAdapter.GetFuture(this);
    }

    public Java.Lang.Object? AttachCompleter(CallbackToFutureAdapter.Completer completer)
    {
        completer.Set(Result.InvokeSuccess());
        return string.Empty;
    }
}
```

### Configuration

**Version:** 9.0.8
net7.0-android

**Platform:** 
- [x] :robot: Android
