Support Aggregate Exceptions

[bobbyg603]

The user shouldn't have to unwind aggregate Exceptions themselves, we should just support this.

https://docs.microsoft.com/en-us/dotnet/standard/parallel-programming/how-to-handle-exceptions-in-parallel-loops

TaskScheduler.UnobservedTaskException += async (sender, e) =>
{
    foreach(var ex in e.Exception.Flatten().InnerExceptions)
    {
        await CrashReporter.Post(ex);
    }
};