Can't call extension methods on `Object`

This is a commonly reported pain-point. Because VB uses `Object` as its dynamic type we disallow extension method lookup on values typed as `Object`. This was done for back-compat concerns as a previously late-bound invocation could become an early-bound extension method invocation when taking a new version of a library, or importing a namespace, etc.

Some have suggested some kind of option which switches off `Object` as the dynamic type and that this would enable this scenario.