[#1452] TX Resubmission-the wallet has to periodically resubmit unmined transactions

[LukasKorba]

• Changelog updated
• The Compact block processor's state machine has been extended to check whether there are any unmined and unexpired transactions, and it attempts to resubmit such transactions every 5 minutes.
• Since Nighthawk servers are no longer functional, demo app's config has been updated to use zec.rocks server

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[HonzaR]

utACK. I just left two comments inline. Other than that, I see some lint warnings, which we could resolve in a separate PR as they seem unrelated to these changes.

[HonzaR]

utACK. The only concern I have is that the current Zashi wallet UX prompts users with a trx submission error and still keeps them on the Send.Confirmation screen, which could lead users to retry the trx confirmation. This new feature might potentially successfully resubmit the first failed one later, resulting in two transactions. We could rethink this Zashi UX when adopting the updated SDK version.

[str4d]

Reviewed de9b8b5

[str4d]

utACK 85c7834