Summary:
A user without SchemaEdit permission was able to reorder pages, since
this changes _grist_Pages, and that table was left under control of
regular access rules. This diff tightens things up, to require
SchemaEdit for all metadata edits. The one remaining exception is
_grist_Attachments, which needs some reworking to play well with
granular access.
Test Plan: extended test
Reviewers: dsagal
Reviewed By: dsagal
Differential Revision: https://phab.getgrist.com/D3025