bd4e6f5b

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

Drop unused QuickCheck + genvalidity-sydtest-aeson deps; rename shadowing

CI flagged two issues:
  - nix-build's -Werror=name-shadowing tripped on 'name' and 'str'
    locals shadowing OptEnvConf re-exports.  Rename to 'pname' and 'input'.
  - nix-build's -Werror=unused-packages tripped on QuickCheck (the only
    user was the Gen module's listOf+suchThat string generator, which
    went away with the JSON config) and genvalidity-sydtest-aeson (its
    sole user was the deleted jsonSpec on MutationDriverConfig).