feat: functions support

[cristeigabriela]

todo: actually add explaination here. wah

[cristeigabriela]

Refactor sqlparse usage to be a crate in the middle with a basic sql evaluator and some basic supported types and a way to bind other types against this crate and thus respectively variables to support making a sql evaluator where each crate just exposes its context to it

bb_sql
evaluator::Evaluator::new()

then bind variables to it as far as the types are supported, and fully recurse

i dont think this should use reflection but rather impls for each type but im not sure. it might get complicated given we also have serde json? maybe we just need to reuse all the same stuff there already. that sounds more reasonable tbh

the evaluator should have the basic sql commands we alrdy defined but also a way to add extra ones at local scope level

maybe a repl would be interesting, long-term