feat(core): support functionArgs in IntoPath

[Damnjelly]

Adds support for functionArgs inside the IntoPath arg of den.provides.forward.
Includes tests for both home manager and nixos (might be a bit overkill?).
Also fixes a typo in the documentation permanance -> permanence

usage example:

  sysPersist =
    { host }:
    {
      class,
      aspect-chain,
    }:
    den._.forward {
      each = lib.singleton class;
      fromClass = _: "sysPersist";
      intoClass = _: host.class;
      intoPath =
        _:
        { config, ... }:
        [
          "environment"
          "persistence"
          config.impermanence.persistence-dir
        ];
      fromAspect = _: lib.head aspect-chain;
      guard = { options, ... }: options ? environment.persistence;
    };

fixed this

[vic]

Thanks @Damnjelly.