- Expose more key derivations to apps via new BackupKey class, as well
as additional APIs on MessageBackupKey and AccountEntropyPool.
- Adjust backup ID derivation from a BackupKey once more (hopefully
the last time).
- iOS: Make incremental MAC chunk size value accessible
- Node: Properly re-export BackupCredentialType through zkgroup module
- Internal change: Use new websocket event handler for attested
connections. This should not produce any difference in behavior,
but if any is observed this might be the cause.
