Remove dynlink and findlib dependencies from goblint-cil library

[sim642]

In https://github.com/ocsigen/js_of_ocaml/issues/1641 it was pointed out that Gobview is trying to link dynamic library linking (Dynlink), which can (besides that issue) also increase Gobview size because Dynlink somehow includes OCaml compiler libraries.

This is completely unnecessary: the goblint-cil library doesn't use dynlink and findlib at all. Only some CIL executable uses those to detect Features at runtime (as opposed to linking them in with -linkall like we do). This PR splits the Feature module to avoid these dependencies.