Modify TapeView to allow SetNextNode to be yielded after everything

[NicolasAG]

As of now, it seems that SetNextNode can be after ToolCalls, but not after Call.
It would be nice to make it consistent and allow SetNextNode after Call as well.

[ollmer]

Can you please create a short example illustrating what happens now when we generate SetNextNode after the Call and what the intended behavior looks like?
I've changed the computation of the next node in #73, and I have some doubts that these changes could already solve the problem, but I need a concrete example to check.

[NicolasAG]

I was looking at the Financial Analyst example at the end of the intro notebook. Particularly inside the generate_steps function of the ActNode. I was wondering if we can change the order of SetNextNode() and AssistantStep(). Just tried it again and it seems to be working regardless of the order...