Change closures to use $app as the first parameter.

Almost always the first parameter is $app therefor it makes little sense
to use `use` part of the closure and having PHP do context switching all
over the place.

This also makes it explicit in the service providers exactly what $app
instance is used.
well the function is a form of a factory, and injecting its dependency seems lik the correct approach? As it is what we would have done in any other case.