[2D] [Animation] New slice on spritesheet starts with bone/weight/geo info from previously created slice from the same sheet

Package Version:
"com.unity.2d.common":"1.0.5-experimental",
"com.unity.2d.animation":"1.0.8-experimental"

Steps to Repro:
- Import new sprite, set it to Multiple
- Create a slice in the Sprite Editor
- Add bones, geo, and weight to the sliced sprite
- Create a new slice on the same sprite

The new slice will start with the bone, geo, and weight info from the previously created slice.