Summary:
With this change, if a comment is added to an ACL formula, then that comment will be offered to the user if access is denied and that rule could potentially have granted access.
The code is factored so that when access is permitted, or when partially visible tables are being filtered, there is little overhead. Comments are gathered only when an explicit denial of access.
Test Plan: added tests, updated tests
Reviewers: dsagal
Reviewed By: dsagal
Differential Revision: https://phab.getgrist.com/D2730