Rebase to 2.16

[dramforever]

There's a new thing for settings that I need to adapt my code to. Does not seem fundamental. Honestly I haven't found the energy to do it.

[dramforever]

tests/search.sh fails like 50% of the time and only if run not in isolation

[dramforever]

tests/search.sh will be fine when NixOS/nix#5754 lands. i've also cleaned up the patch for nix-environment.patch though it was not particularly pretty.

[dramforever]

(by 'lands' i mean when i inevitably have to rebase to 2.17)