fix(wrapperModules.fish): fix abbreviation argument order

[iynaix]

Currently, doing

abbreviations = {
  "--help" = {
    expansion = "--help | bat --plain --language=help";
    position = "anywhere";
  };
};

generates

abbr --add --help  --position anywhere    "--help | bat --plain --language=help"

which results in abbr --help being called instead of the abbreviation being set.

This fix changes it to generate the following instead.

abbr --add  --position anywhere    -- --help "--help | bat --plain --language=help"

I've also wrapped the shellAliases and abbreviations to only be evaluated in interactive shells. Any output produced by fish breaks completion generation, since it gets prepended to the python completion generator: https://github.com/NixOS/nixpkgs/blame/6368bc923cec55a5f78960ade0cb4dd99580e087/nixos/modules/programs/fish.nix#L273

I've also set the abbreviation position to "command" as outlined in #582. If this is not desired, I can remove this change.

@ormoyo