Function ICU4XLocaleFallbacker_for_config

#[no_mangle]
extern "C" fn ICU4XLocaleFallbacker_for_config<'a, 'temp>(
    this: &'a ICU4XLocaleFallbacker,
    config: ICU4XLocaleFallbackConfig<'temp>,
) -> DiplomatResult<Box<ICU4XLocaleFallbackerWithConfig<'a>>, ICU4XError>