Remove Reconstruct_question_marks phase and Question_mark nodes from the AST

[W95Psp]

Resugaring question marks is not very useful, instead we prefer to treat them as "normal" early returns.
That simplifies a few things.

Also, in the context of a function that takes &mut inputs, question marks breaks for us. We rewrite a function &mut T -> Result<U, E> as T -> (Result<U, E>, T). In this settings, question mark expressions are useless: we need to rewrite e? so that if e is Err(e'), then we return (s, e) with s the "state" U. This cannot be captured with a question mark.

Status

Question marks are used by the proverif backend.
But question marks are broken, as noted above: &mut inputs functions + question mark are broken.
So we need to remove the need of question marks from proverif.

[github-actions]

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[github-actions]

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[W95Psp]

Still relevant

[W95Psp]

The proverif backend makes use of this phase and makes use of the Question_mark node.