feat(tests): add test utils (tlib) v2

[zenoli]

This is an extension of #439 which I refer to as "V1".

V1 Syntax

(runTest "if nix-direnv is enabled then lib/nix-direnv.sh should exists" (
  let
    wrapper = self.wrappers.direnv.wrap {
      inherit pkgs;
      nix-direnv.enable = true; 
    };
  in
  [
    (isDirectory (getDotdir wrapper))
    (isFile "${getDotdir wrapper}/lib/nix-direnv.sh")
  ]
))

V2 Syntax

The V2 syntax is 100% backwards compatible to V1. But it can also do this:

(runTest
  {
    name = "if nix-direnv is enabled then lib/nix-direnv.sh should exists";
    config.nix-direnv.enable = true;
  }
  (wrapper: [  # <-- this wrapper has the above config applied
    (isDirectory (getDotdir wrapper))
    (isFile "${getDotdir wrapper}/lib/nix-direnv.sh")
  ])
)

[BirdeeHub]

Sorry for any merge conflicts you get, I'm adding the ..., hopefully it lets you rebase and doesn't yell at you because they are the same?

[zenoli]

No worries. Thx for
Letting me know

[zenoli]

Closing this as the final version is now here #439