There seems to be some changes on how wrapped binaries are implemented
on nixpkgs. This broke the nnn tests since the tests were coupled with
the old implementation.
This commit fix the tests, and also make it less coupled by just testing
if the bookmarks/plugins/environment variables are available.
nnn is a terminal file manager.
It is configured mostly using environment variables, so the way I
found it to avoid needing to write either shell specific code or
using `home.sessionVariables` (that would need to make the user
relogin at every configuration change) is to wrap the program using
`wrapProgram`.
