Store interactions before adding them so that order is maintained when interactions add other interactions.
Store interactions before adding them so that order is maintained when interactions add other interactions.

Summary: As per the spec: https://material-motion.github.io/material-motion/starmap/specifications/runtime/MotionRuntime-addInteraction

Reviewers: O2 Material Motion, O4 Material Apple platform reviewers, #material_motion, chuga

Reviewed By: O4 Material Apple platform reviewers, chuga

Tags: #material_motion

Differential Revision: http://codereview.cc/D2980

material-motion/material-motion-swift,material-motion/material-motion-swift