test.api: use Hydra perl dependencies to run `api-test.pl`

Dependencies

• [2] 5QYMALGU Fix Perl error in tests.api
• [3] WQ2VQ7H3 Use hydra-module.nix in the tests
• [4] LZVO64YG Merge in the first bits of the API work
• [*] T4LLYESZ * Nix expression for building Hydra.

Change contents

• replacement in release.nix at line 222
  [3.1740]→[2.321:405](∅→∅)
  − $machine->mustSucceed("su - hydra -c 'perl ${./tests/api-test.pl}' >&2");
  [3.1740]

  [3.1720]
  + $machine->mustSucceed("su - hydra -c 'perl -I ${build.${system}.perlDeps}/lib/perl5/site_perl ${./tests/api-test.pl}' >&2");