bats: move installCheck into passthru.tests
bats: move installCheck into passthru.tests

I happily painted myself into a corner when converting bats to use
resholve. Since resholve tests itself with bats, all updates to
resholve now require rebuilding bats. The build itself is quick, but
the tests take a few minutes; moving them into passthru saves time. :)

NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs,NixOS/nixpkgs