[ATR-24897] Additional trigger runtime navigation sanity validation. Nodes with large numbers of edges.

Allows the printing of WARNING messages if there are nodes in the trigger navigation graph which are cause for concern, notably.

If a node contains > 100 ElementLinks to other nodes in (or out of, e.g. features) the graph. This will pick up cases of massive fan-in, where one node links to a large number of direct parents. Or cases of an extreme number of external links. Or a mix of the two.

If there are > 100 nodes who are direct downstream children of a node (and hence who are all in possession of their own ElementLink to the node in question). This will pick up cases of massive fan-out.

Other checks may be needed in the future to investigate events with exceptionally large navigation, as these two will only pick up on certain dark patterns.