improve topology view stability for short-lived nodes

[rade]

Short-lived connections can make the topology view quite unstable.

Related:

• Missing connections from short-lived processes #1250 - for capturing more short-lived connections in the first place.
• improve topology view stability for short-lived connections #1674 - same issue but for edges
• Dancing nodes when nodes are added/removed #1033 - dancing nodes

[rade]

As with #1674, a notion of decay might work here. I don't think it can be the same decay as edges though since, unlike edges, nodes take up space in the UI, so long decays of nodes when there are lots of short-lived containers would fill the screen pretty quickly.

[rade]

Thinking about this... node decay would probably be useful in other views/modes too.