MergeTree: Deprecate segmentGroups and ack on ISegment

[anthony-murphy]

Deprecate segmentGroups and ack on ISegment
The SegmentGroupCollection class, along with the segmentGroups property and ack function on segments, are not intended for external use.
These elements will be removed in a future release for the following reasons:

• There are no scenarios where they need to be used directly.
• Using them directly will cause eventual consistency problems.
• Upcoming features will require modifications to these mechanisms.