0c98514f

By: Tom Sydney Kerckhove <syd@cs-syd.eu>

Expose mutation Nix functions as passthru on sydtest, not top-level attrs

The addManifest, compileMutationReport, assertMutationScore, runMutations,
and makeMutationReport values are Nix functions, not packages. Move them
from mutationNixPackages (a top-level attr in the package set) to passthru
on the sydtest derivation.