Fix traversal when deleting nodes

[adamgerhant]

Closes #3357

[Keavon]

As mentioned on Discord, we actually need to not delete any other nodes except the Add node in the annotated screenshot in your PR description. Sorry for the confusion. Marking as draft for the moment.

[Keavon]

Basically, we should do this:

Step 1. Delete the node on its own and reconnect it using the current system
Step 2. Check if we left behind a chain of nodes from our other (secondary) inputs which now are disconnected and each one were sole dependents of the now-deleted node's secondary inputs
Step 3. Delete those if so, but if any node that wasn't directly connected to the now-deleted node is still around, that acts as the dependent to preserve those nodes

Correct cases:

Before	After

[Keavon]

@adamgerhant

In this file:

Twirl.graphite.txt

Deleting the Transform node incorrectly deletes way too much:

capture_20_.mp4

Only the nodes in the red box should be deleted in this case.

[adamgerhant]

Should be fixed now that traversal accounts for the nodes connected to primary input not getting deleted.