Fixes#10075Fixes#10013
When interpolating, we were only maintaining the last known slice index.
If you had sibling slices then you could lose your slice index when
exiting the slice. The resulting behavior was that no some runs the
computed key would be: "slice.0.attr" and on others would be
"slice.attr", the latter being incorrect.
We now maintain a list of slice indexes so that as we unnest, we
properly restore the old value.
Surprisingly unrelated to the graph but the shadow graph caught this
which is great. :)
b3f80b9469