Zebra v1.0.0-alpha.4

Zebra's latest alpha starts our work on NU5 and fixes several security issues.

Some notable changes include:

​Added

Network Upgrade 5

• Add some NU5 constants to zebra (#1823)
• Start work on transaction version 5 (#1824)

Metrics

• Add Grafana dashboards (#1830)
• Add Zebra version info to metrics (#1900)
• Add message type tag to message metrics (#1900)

Changed

• ZIP-215 Explicitly Defining and Modifying Ed25519 Validation Rules (#1811)
• Metrics renaming to enable node interoperability (#1900)
  • Renaming metrics breaks existing Grafana configs
• Rename config network.new_peer_interval to crawl_new_peer_interval (#1855)
  • This change includes a backwards-compatibility alias, so existing configs do not need to be updated

Fixed

Code Style

• Apply nightly clippy suggestions (#1834)

​Documentation

• Re-enable zebra.zfnd.org deployment (#1792)
• Document and log trailing message bytes (#1888)
• Move design/data-flow to rfcs/drafts (#1825)
• Document how inbound connections are added to the CandidateSet (#1852)

Hangs and Panics

• Fix a peer DNS resolution edge case (#1796)
• Stop sending blocks and transactions on the first error (#1818)
• Revert a connection refactor that caused frequent hangs (#1803)

​Testing

• Avoid acceptance test port conflicts (#1812)
• Re-enable the checkpoint verifier restart tests (#1837)
• Adjust the crawl interval and acceptance test timeout (#1878)
• Explicitly auto-delete additional cache disks (#1859)

Security

• Reduce inbound concurrency to limit memory usage (#1881)
• Verify proof-of-work in the checkpoint verifier (#1882)
• Implement outbound connection rate limiting (#1855)
• Document that the configured Zcash listener IP address is advertised to remote peers (#1891)