Macro mz_sql::session::vars::value::impl_value_for_simple

macro_rules! impl_value_for_simple {
    ($t: ty, $name: literal) => { ... };
}

Macro to implement Value for simpler types, i.e. ones that already implement FromStr and ToString.

Note: Macros can be hot garbage, if at any point folks think this is too complicated please feel free to refactor!