wb | unify on-disk genesis layout
Both `create-staked` and `create-testnet-data` converge on the create-testnet-data key-directory layout:
- pools-keys/poolN/{cold,kes,vrf,opcert}.{skey,vkey,cert,counter}
- stake-delegators/delegatorN/
- byron-gen-command/
- drep-keys/
- utxo-keys/
Details:
- reshapes create-staked's flat pools/coldN.skey output into pools-keys/poolN/ subdirs.
- renames stake-delegator-keys -> stake-delegators.
- create-testnet-data drops its symlink-creation block and the `link_keys` helper (no longer needed under the native layout).
- Removes `Massage_the_key_file_layout_to_match_AWS`, `key_depl` and `key_genesis`.
- `derive-from-cache-jq` symlinks the new key dirs in a single loop.
- Consumers (nomad/cloud.sh, service/{generator,nodes}.nix, workload/voting.nix) point at the new key paths.
Genesis file names are unchanged here.