fix: parse keys with 0x prefix

[LGLO]

Description

Our registration-signatures command outputs:

{"spo_public_key":"0x08accadc8b60a5f519ee74ab144ada6993709f5479152f9217688889d8a2db2e","spo_signature":"0x040a8b9f336986fe5cea10a3bfcd6fb4f84dceda8e00ca23eee6e28af0605fb86fd96b41746df159b318b5075e067ce30e67d2bf5fef3e21f01a48325e375a06","sidechain_public_key":"0x039799ff93d184146deacaa455dade51b13ed16f23cdad11d1ad6af20103391180","sidechain_signature":"0xf0905c8d5a4db6075f76f6628282b3e257ffa1184ba2e35cd34415968d360d7452c981d171b4f22489690994a46026c1c1801df3e83f1038d4f20bb8affdfbcd"}

, so it is not nice to not accept 0x prefix at input.
With this modification such command is accepted:

target/debug/partner-chains-node smart-contracts register --genesis-utxo c389187c6cabf1cd2ca64cf8c76bf57288eb9c02ced6781935b810a1d0e7fbb4#0 --registration-utxo c389187c6cabf1cd2ca64cf8c76bf57288eb9c02ced6781935b810a1d0e7fbb4#2 \
--spo-public-key 0x08accadc8b60a5f519ee74ab144ada6993709f5479152f9217688889d8a2db2e \
--spo-signature 0x08accadc8b60a5f519ee74ab144ada6993709f5479152f9217688889d8a2db2e08accadc8b60a5f519ee74ab144ada6993709f5479152f9217688889d8a2db2e \
--partnerchain-signature 0x08accadc8b60a5f519ee74ab144ada6993709f5479152f9217688889d8a2db2e08accadc8b60a5f519ee74ab144ada6993709f5479152f9217688889d8a2db2e \
--partnerchain-public-keys 0x039799ff93d184146deacaa455dade51b13ed16f23cdad11d1ad6af20103391180:0xe85534c93315d60f808568d1dce5cb9e8ba6ed0b204209c5cc8f3bec56c10b73:0xcdf3e5b33f53c8b541bbaea383225c45654f24de38c585725f3cff25b2802f55 --payment-key-file dev/local-environment/configurations/partner-chains-nodes/partner-chains-node-4/keys/payment.skey

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.

[kpinter-iohk]

Good catch, thank you for the fix!