Enable depth peeling only for 3d renderers
Summary: Fixes T26981
Test Plan: Manually tested both multiple segmentations in 2d and complex translucent scenes in 3d.
Reviewers: O1 MITK Reviewer Group I, floca
Reviewed By: O1 MITK Reviewer Group I, floca
Maniphest Tasks: T26981
Differential Revision: https://phabricator.mitk.org/D323