R1:3058cae4b82e

Allow task statuses to specify that either "comments" or "edits" are "locked"

Summary:
Ref T13249. See PHI1059. This allows "locked" in `maniphest.statuses` to specify that either "comments" are locked (current behavior, advisory, overridable by users with edit permission, e.g. for calming discussion on a contentious issue or putting a guard rail on things); or "edits" are locked (hard lock, only task owner can edit things).

Roughly, "comments" is a soft/advisory lock. "edits" is a hard/strict lock. (I…