Network Sustainability Mechanism - ZIP 234 & 235 implementation

[mariopil]

Motivation

This PR implements ZIP-234 and ZIP-235.

Specifications & References

ZIP-234, ZIP-235

Solution

This PR is implemented above #8930 which implements the ZIP-233. It smoothes the issuance curve (ZIP-234) and introduces the split between miner fees (40%) and the amount that is burned (60%, ZIP-235). Some of the code used in the block semantical verification for block subsidy calculation has been moved into the write task, as now the block subsidy calculation relies on the current amount of money_reserve which is obtained from pool value balance at height-1- therefore the previous block must be already present at least in the non-finalized best chain.

Tests

For testing purposes, a local testnet network was set up. It contained two nodes—a zebra and a zcashd one (with the ZIP-234 & 235 implemented, too, PR zcash/zcash#6970). A transaction in a new format containing the burn_amount field was created and added to the block by zcashd. The zebra node synced with zcashd without any errors and accepted the block.

A couple of unit tests were also added.

Follow-up Work

PR Author's Checklist

• The PR name will make sense to users.
• The PR provides a CHANGELOG summary.
• The solution is tested.
• The documentation is up to date.
• The PR has a priority label.

PR Reviewer's Checklist

• The PR Author's checklist is complete.
• The PR resolves the issue.