cardano-testnet: use new output of "transaction submit"

[smelc]

[!WARNING]

Needs https://github.com/IntersectMBO/cardano-cli/pull/925

Description

Test this new additional output of transaction submit: https://github.com/IntersectMBO/cardano-cli/pull/925

Checklist

• [X] Commit sequence broadly makes sense and commits have useful messages
• [X] New tests are added if needed and existing tests are updated.
• [X] Self-reviewed the diff