Unwrap TargetInvocationException

[manfred-brands]

Fixes #4481

Code for

Assert.That(new Dictionary<string, string>(), Does.ContainKey(null!));

Now results in:

  Message: 
    System.ArgumentNullException : Value cannot be null. (Parameter 'key')

  Stack Trace: 
    Dictionary`2.FindValue(TKey key)
    Dictionary`2.ContainsKey(TKey key)

There are two methods in Reflect.cs ending in WithTransparentExceptions.
These are used in Assert.Throws and equivalents and were not modified to unwrap.
Unwrapping all InnerExceptions would make it impossible to catch a TargetInvocationException thrown by user code.

This means that to validate that the Does.ContainKey(null!) throws an ArgumentNullException we
first have to test for the TargetInvocationException.
Beside testing NUnit, not many people will Assert an Assert.

Assert.That(() => Assert.That(new Dictionary<string, string>(), Does.ContainKey(null!)),
            Throws.TargetInvocationException.With.InnerException.InstanceOf<ArgumentNullException>());

[OsirisTerje]

I believe this looks good now.

[OsirisTerje]

Feel free to merge