Document and regroup flags that enable SMT patterns

[TWal]

In #54, we add a command enable_bytes_well_formed_smtpats that enables a set of SMT patterns in lemmas about bytes_well_formed. In the review, @qaphla make the remark that if we were to add more commands like this, it would be good to regroup and document them.

Although this is not needed right now, I am opening this issue to remember that when we add more flags in the future.