[Macros] Reduce generated code for field conversions

[GnomedDev]

This moves all the implementations of vec_tuple_2_to_hash_map into calling the actual function, now iter_ to allow for these generics. This then adds an early return for the iterator having no items, which gets rid of the somewhat silly vec![].into_iter().collect() and HashMap::from_iter([]) code.

This also does the same for wrap_option, removing the None.map(Duration::from_secs) that was in CooldownConfig.