Transaction-related backports for v14.0

This MR contains a backport of !3615 (merged) and !3630 (merged). While these changes had already landed on 14-0-stable, we didn't properly follow release procedures there and thus the changes were reverted. This commit here simply reintroduces all these commits and thus effectively reverts the revert.

All are fixes to issues with strong consistency/transactional voting.