[proofs] [dot] New way to traverse the proof when printing a .dot DAG (#8610)

[proofs] [dot] New way to traverse the proof when printing a .dot DAG (#8610)

Change the way cvc5 traverse and print the proof when --proof-dot-dag option is used. The main change is related to the way the printer tracks visited proof nodes. The new conditions are:

- If the proof node has already been visited inside the current scope.
- If the proof node is closed (i.e. does not contains a subproof whose rule is ASSUME) and has already been visited (here the condition is global and the scope doesn't matter).

Signed-off-by: Vinícius Braga Freire vinicius.braga.freire@gmail.com