Add complex expression support for DbFunction parameters

[AndriySvyryd]

This would be especially useful in cases where the parameters don't come from a query root and therefore cannot be rewritten using let/Select like

from r in context.GetCustomerOrderCountByYear(() => context.AddValues(-2, 3))
orderby r.Count descending
select r

[pmiddleton]

@AndriySvyryd Can you show an example of what you are proposing? I am not quite understanding what you are looking for.

[AndriySvyryd]

@pmiddleton It's what you had in the last PR, but we decided to remove it for now since it doesn't work with expressions that contain navigations or shadow property references.

[pmiddleton]

Ok got it. That makes sense now.