Fix issue with annotations and nested extensions

[matt-sheets]

Previously any annotations on a nested extension would be ignored. The code will now properly propagate the annotations to the types created by the extensions.

[dburgener]

Can we add another test case for something like this?

domain foo {
    resource bar {}

    @alias(baz)
    extend bar {}
}

And make sure the alias applies appropriately

[dburgener]

Merged, thanks!