fix(circ): Fix issues and refactor the package

* Use `fetchFromGitHub` and set `rev`
* Set more appropriate version
* Replace `with pkgs` with explicit reference to each package
* Replace `cargoHash` with `cargoLock`
* Fix build features by looking at the Cargo.toml file of the project
* Update `meta`

Also:
* Re-enable the package in `shell.nix`

Author: PetarKirov