local-dev-cluster: publish the keys on explorer machine

[denisshevchenko]

Currently the cluster local-dev-cluster contains three machines a, b and c for core nodes and explorer machine for cardano-explorer-node and for transaction generator as well. But we need both keys and certificates to be able to run transaction generator (because it should sign generated transactions). Particularly, we need:

1. delegate-keys.000.key
2. delegate-keys.001.key
3. delegate-keys.002.key
4. delegation-cert.000.json

Currently these keys/certificate aren't presented on explorer machine by default, so they were copied to explorer machine manually, using nixops scp. So, nix scripts should be improved in order these keys/certificate will be published to explorer machine automatically during deployment.

[denisshevchenko]

@jbgi ^

[CodiePP]

in epic: input-output-hk/iohk-monitoring-framework#323

[denisshevchenko]

Done.

Now required certificate and keys will be copied to explorer machine automatically, during nixops deploy command. They are:

1. /var/lib/keys/cardano-node-delegation-cert - delegation certificate, will be passed to --delegation-certificate CLI parameter.
2. /var/lib/keys/cardano-node-signing-gen - first signing key delegate-keys.000.key, will be passed to --sig-key CLI parameter.
3. /var/lib/keys/cardano-node-signing-src - second signing key delegate-keys.001.key, will be passed to --sig-key CLI parameter.
4. /var/lib/keys/cardano-node-signing-rec - third signing key delegate-keys.002.key, will be passed to --sig-key CLI parameter.

Only roles/explorer.nix script was changed (both in local-dev-cluster and in remote-dev-cluster).

These keys will be passed to cardano-cli generate-txs during its start (see #28).