Release v19.51.2

Fixed

• A projection future is no longer lost when a catch-up or replay write fails. While a projection catches up or replays, a write that resolves a future is now made immediately with a known outcome instead of being buffered, and the future is removed only after that write succeeded. Failed writes are reported as failed partitions. (#4753)
• Failures of buffered MongoDB projection writes during catch-up and replay are reported exactly once, and writes queued behind a failed batch are still written. (#4753)
• A projection future stays registered if storing its resolution fails, instead of disappearing from memory while it is still stored. (#4753)