Star ghost depth
Implement changes to push the stellar ghost task deeper in the tree as this was found to be one of the bottlenecks in #696 (closed). This is part of the safe changes introduced in !1217 (closed).
Implement changes to push the stellar ghost task deeper in the tree as this was found to be one of the bottlenecks in #696 (closed). This is part of the safe changes introduced in !1217 (closed).