2.7.4 Backport CBG-882 - Align channels query ORDER BY with index

The channels query ORDER BY that was added for safety results in performance degradation for very large channels. It should be rewritten to align with the index definition:

ORDER BY [op.name, LEAST(meta(`write`).xattrs._sync.sequence, op.val.seq),IFMISSING(op.val.rev,null),IFMISSING(op.val.del,null)]

Also need to review performance scenarios to understand why this degradation wasn't identified there.