fix nullability of AssemblyEnumerator.GetTypes

[SimonCropp]

• ReflectionTypeLoadException.Types returns Type?[] https://learn.microsoft.com/en-us/dotnet/api/System.Reflection.ReflectionTypeLoadException.Types?view=net-9.0 to return type of AssemblyEnumerator.GetTypes is incorrect
• ReflectionTypeLoadException.LoaderExceptions returns a Exception?[] https://learn.microsoft.com/en-us/dotnet/api/system.reflection.reflectiontypeloadexception.loaderexceptions?view=net-9.0 so the null check is a no-op. i assume the intent is to "log a warning and continue with loaded types if there are LoaderExceptions"
• fixed a bug where GetAssemblyInfo would redundantly attempt to IsDerivedAttributeDefined for a null value, and then catch the result null ref excpetion

[Youssef1313]

This is a change in behavior.

Previously if type was null, we will go through the try, which will fail, then we get into the catch that will fail due to t.FullName (it will throw NullReferenceException).

The original intent is to probably ignore types that failed to load, but that as well wasn't a good design decision.

I think it's best in v4 if we just not catch any ReflectionTypeLoadException and let everything fail.