openssl-chacha: Split into multiple outputs

Mainly done because of this in all-packages.nix:
````
  cipherscan = callPackage ../tools/security/cipherscan {
    openssl = if stdenv.system == "x86_64-linux"
      then openssl-chacha
      else openssl;
  };
````
... and inside cipherscan we want to refer to `openssl.bin`