Support `@differentiable` function conversion for `init` references, in
addition to `func` references and literal closures. Minor usability improvement.
Resolves SR-12562.
The name of the module is encoded into the type name. The module name
is not `null` on Windows, which would fail to match the name. It is
possible to make the test less overly-constricted, but setting the
module name to null is simpler and avoids more regex matching.
Support `@differentiable` function conversion for `init` references, in
addition to `func` references and literal closures. Minor usability improvement.
Resolves SR-12562.
