Summary:
- When Public Edit access is enabled, Access Rules page shows a warning and
prevents saving rules.
- When any ACL rules are present, attempts to set Public access to Editor role
get downgraded to Viewer role, with a warning notification.
- No checks are made on the server side, so the combination may be achieved via
the API (but we may block it in the future).
Test Plan: Added a test case.
Reviewers: paulfitz
Reviewed By: paulfitz
Differential Revision: https://phab.getgrist.com/D2767