Commit draft segment change requests

[emyller]

User story:

As a dashboard user, while reviewing a change request, I can approve and publish (commit) the changes proposed in segments.

We need to replace the existing logic for publishing segment changes so that it will:

• Make a copy of the live segment for historical purposes with a new Segment.clone method, and get rid of SegmentCloneService and existing Segment.*clone methods entirely. The new function must create a revision of the segment, as well as its nested rules and conditions.
• Overwrite attributes of segments, then replace all nested rules and conditions.

[emyller]

The new clone code was implemented in this effort, later replaced with #5768 (parent of this issue).