Function resolve_instrument_families 

pub fn resolve_instrument_families(
    configured: &Option<Vec<String>>,
    inst_type: OKXInstrumentType,
) -> Option<Vec<String>>

Resolves instrument families for a given instrument type.

Returns Some(families) when the type supports family filtering, or None to skip the instrument type entirely (Option without configured families). An empty vec means no family filter is needed (Spot, Margin).