Better search when dragging out from a sequence port in VisualScript

[Jummit]

Godot version: 3.1.1

Issue description: The new node search in VisualScript has plenty of nodes that use sequence ports that the search when dragging out of a sequence port lacks. At least the nodes with a sequence port should be visible there. I would even go as far as saying that the drag-out search should be identical to the node search, just that it automatically connects the sequence port if there is one. That's how it's done in UE4 at least, and I see it as a faster workflow as searching by ctrl+f all the time.

Steps to reproduce: Make a new VisualScript and hit ctrl+f or do "Search Nodes".

[swarnimarun]

As I mentioned in the PR.

Visual Script is not only supposed to be fast but also self-explanatory, All hints should make sense. Otherwise, it will be confusing to pull a node from the list, link it and figure out that it gives runtime error..

So we have to focus on both simplicity and ease of understanding and implementation while improving, efficiency.

In future we can probably use ClassDB for classinfo and extra details to make it a lot more powerful which would be a lot of work so PRs are welcome.