Support Global Exception Handling Mechanism for .NET MAUI

Discussed in https://github.com/dotnet/maui/discussions/653

^{Originally posted by AmSmart April 5, 2021} With the new host model in .NET Maui, will we get a straightforward way of catching exceptions?</div>

Currently this is possible in WPF/WinForms via:

AppDomain.CurrentDomain.UnhandledException += (sender, error) =>
{
    MessageBox.Show(text: error.ExceptionObject.ToString(), caption: "Error");
};

The ask of this issue is to enable AppDomain.CurrentDomain.UnhandledException for MAUI based applications to support a global exception handling mechanism.

I looked into the Windows MAUI WinUI3 end of things, and there appears to be a potential bug with the DispatcherQueue which prevents the application from being sent to the AppDomain.CurrentDomain.UnhandledException: https://github.com/microsoft/microsoft-ui-xaml/issues/5221

cc/ @hartez @mattleibow

Blazor Hybrid

Cross linking https://github.com/dotnet/aspnetcore/pull/40765 which handles the case of WPF/WinForms in Blazor Hybrid. If there’s a canonical way to do global exception handling (like we have in WinForms/WPF), we need to ensure .NET MAUI Blazor Hybrid is able to integrate with it directly.

Blazor Hybrid MAUI tracking issue: https://github.com/dotnet/maui/issues/4441

• https://github.com/dotnet/aspnetcore/pull/40765
• https://github.com/microsoft/microsoft-ui-xaml/issues/5221
• https://github.com/dotnet/maui/issues/4441
• MAUI: enable AppDomain.CurrentDomain.UnhandledException for MAUI based applications to support a global exception handling mechanism