Summary:
This implements row-level access control for outgoing messages, replacing the document reloading placeholder that was there before.
* Prior to broadcasting messages, GranularAccess is notified of actions+undo.
* While broadcasting messages to different sessions, if we find we need row level access control information, rows before and after the change are reconstructed.
* Messages are rewritten if rows that were previously forbidden are now allowed, and vice versa.
The diff is somewhat under-tested and under-optimized. Next step would be to implement row-level access control for incoming actions, which may result in some rejiggering of the code from this diff to avoid duplication of effort under some conditions.
Test Plan: added test
Reviewers: dsagal
Reviewed By: dsagal
Differential Revision: https://phab.getgrist.com/D2670
