Re-visit "child-of-root" space view spawning heuristics

[Wumpf]

Largely a follow-up of:

• Re-engineer the space-view heuristics engine #4388

There's a bunch of cases where we treat child entities of the root special for the purpose of spawning space views:

• 3D space views
  • NOTE: Improve 2d spawn heuristics #5087 removes this for 2D views
• time series space views
  • Spawns space views iff there's several child of root which don't have timeseries indicators themselves but have children that do
  • See plots demo why this is needed: We expect separate plots for each child of the root node. Each plot in turn contains several entities

This is problematic since it's a fairly complicated heuristic both for a user to understand and for our implementation to maintain!
On the flip side it allows to easily crate many space views without user ui interaction & logging anything extra!

Mitigation / strategies for removal:

• Spawn a 3D space view wherever there's ViewCoordinate, don't spawn in the "remaining space" if this wouldn't add any more entities
• Plots seems harder: We could just accept a single plot or a plot for each entity (this breaks the plots demo as-is)
• ... TODO: would the above be enough?