Allow Debug Logging of Logits

[lapp0]

What behavior of the library made you think about the improvement?

If the model generates bad results we currently have no idea why. E.g.

• https://github.com/outlines-dev/outlines/issues/612#issuecomment-1928014413
• https://github.com/outlines-dev/outlines/issues/580#issuecomment-1909236093

How would you like it to behave?

For each generation step, we should have an optional debug log of

• 1. The softmaxed logits and decoded representation of the top N tokens
• 2. The softmaxed logits of all special tokens (namely EOS)