feat: improve handling of payment key argument and add documentation for some other fields

[LGLO]

Description

./partner-chains-node smart-contracts init-governance -c 61ca664e056ce49a9d4fd2fb3aa2b750ea753fe4ad5c9e6167482fd88394cf7d#0 -k payment.vkey -g e8c300330fe315531ca89d4a2e7d0c80211bc70b473b1ed4979dff2b
Error: Application("Could not read private key file. Reason: Unsupported key type: PaymentVerificationKeyShelley_ed25519. Expected a signing key")

Instead of failing transaction because of missing funds when verification key is used in place of signing key.

2. Added help messages to params in register and deregister:

./target/debug/partner-chains-node smart-contracts register --help
Register candidate

Usage: partner-chains-node smart-contracts register [OPTIONS] --genesis-utxo <GENESIS_UTXO> --registration-utxo <REGISTRATION_UTXO> --payment-key-file <PAYMENT_KEY_FILE> --partner-chain-public-keys <PARTNERCHAIN_KEY:AURA_KEY:GRANDPA_KEY> --partner-chain-signature <PARTNER_CHAIN_SIGNATURE> --spo-public-key <SPO_PUBLIC_KEY> --spo-signature <SPO_SIGNATURE>

Options:
  -O, --ogmios-url <OGMIOS_URL>                                            [default: http://localhost:1337]
      --genesis-utxo <GENESIS_UTXO>                                        Genesis UTXO of the partner-chain
      --registration-utxo <REGISTRATION_UTXO>                              UTXO that will be spend when executing registration transaction, part of the registration message
  -k, --payment-key-file <PAYMENT_KEY_FILE>                                Path to the Cardano Signing Key file used sign transaction(s) and pay for them
      --partner-chain-public-keys <PARTNERCHAIN_KEY:AURA_KEY:GRANDPA_KEY>  Colon separated hex strings representing bytes of the Sidechain, Aura and Grandpa public keys
      --partner-chain-signature <PARTNER_CHAIN_SIGNATURE>                  Hex string of bytes of the registration message signature by partner-chain key, obtained by 'registration-signatures' command
      --spo-public-key <SPO_PUBLIC_KEY>                                    Hex string representing bytes of the Stake Pool Verification Key
      --spo-signature <SPO_SIGNATURE>                                      Hex string of bytes of the registration message signature by main chain key, obtained by 'registration-signatures' command
  -h, --help                                                               Print help
  -V, --version                                                            Print version

Checklist

• Commit sequence broadly makes sense and commits have useful messages.
• New tests are added if needed and existing tests are updated.
• Relevant logging and metrics added
• CI passes. See note on CI.
• Any changes are noted in the changelog.md for affected crate
• Self-reviewed the diff

Note on CI

If your PR is from a fork, the necessary CI jobs won't trigger automatically for security reasons.
You will need to get someone with write privileges. Please contact IOG Partner Chains developers to do this
for you.