NoSimpleLetBody should report destructuring for named patterns in other modules

[jfmengels]

At the moment, the rule doesn't report the destructuring of single variant constructors when we don't know whether the type has any phantom types (as that could be the purpose of the destructuring).

This correctly doesn't get reported.

type A b = A String
a = let (A b) = xyz
    in A b

but we only gather information about constructors from the current module. If a single-variant custom type from another module or from a dependency is used in such a way when it doesn't have a phantom type variable, then we should report it.

module SomeModule exposing (A(..))
type A b = A String

-- other module
import SomeModule exposing (A(..))
-- should be simplified
a = let (A b) = xyz
    in A b