Wrapped libraries support

[kit-ty-kate]

This tool doesn't currently support dune's way of renaming modules to wrap libraries and currently only see the cmti files if the libraries are first unwrapped.

Steps to reproduce:

$ cat dune-project
(lang dune 2.0)
(package (name dead))
$ cat dune
(library (public_name dead) (modules lib_mod) (wrapped true))
(executable (public_name dead_bin) (modules dead_bin) (libraries dead))
$ cat lib_mod.ml
let dead () = print_endline "dead code"
let live () = print_endline "live code"
$ cat lib_mod.mli
val dead : unit -> unit
val live : unit -> unit
$ cat dead_bin.ml
let () = Dead.Lib_mod.live ()
(* let () = Lib_mod.live () *)

As-is (wrapped library), scanning the project leads nowhere, as if there was no dead code:

$ dune build
$ dead_code_analyzer _build/default/
Scanning files...
 [DONE]

.> UNUSED EXPORTED VALUES:
=========================

Nothing else to report in this section
--------------------------------------------------------------------------------


.> UNUSED METHODS:
=================

Nothing else to report in this section
--------------------------------------------------------------------------------


.> UNUSED CONSTRUCTORS/RECORD FIELDS:
====================================

Nothing else to report in this section
--------------------------------------------------------------------------------

But as soon as you turn (wrapped ...) to false and switch the commented code in dead_bin.ml, then the dead code is actually detected instantly:

$ dune build
$ dead_code_analyzer _build/default/
Scanning files...
 [DONE]

.> UNUSED EXPORTED VALUES:
=========================
_build/default/lib_mod.mli:1: dead

Nothing else to report in this section
--------------------------------------------------------------------------------


.> UNUSED METHODS:
=================

Nothing else to report in this section
--------------------------------------------------------------------------------


.> UNUSED CONSTRUCTORS/RECORD FIELDS:
====================================

Nothing else to report in this section
--------------------------------------------------------------------------------

Moved from #16 (comment)

[fantazio]

I have a fix in fantazio:fix_wrapped. I'll wait for #31 to be merged before opening the fix's PR (the fix branch includes commits from the existing PR). This is to keep PRs of reasonable size for easier reviews.