Dropping nodes onto a wire, to insert it inline, sometimes doesn't work for secondary inputs

[Keavon]

We can usually drop a node onto a wire to get it to be inserted (via its primary input and output).

capture_17_.mp4

There are expected cases when this doesn't occur: if the node is over multiple wires, there'd be no one non-arbitrary choice, when the dragged node doesn't have a primary input or output, and when multiple nodes are being dragged. This issue isn't about these expected cases.

But sometimes situations arise where we can't drop a node in a place where it should clearly go:

capture_24_.mp4

This seems to happen often with secondary inputs, but it still works sometimes with them too. Here is a simple reproduction file:

reproduction.zip

[Keavon]

CC @adamgerhant

[0HyperCube]

editor/src/messages/portfolio/document/utility_types/network_interface.rs:5572
Could not get upstream output in insert_node_between