bug: decode_multiple can overflow

[iqdecay]

During a fuzzing campaign, it turned out that this test panics with an attempt to add with overflow:

        let param_types = vec![ParamType::Enum {
            variants: EnumVariants::new(vec![ParamType::Struct {
                fields: vec![
                    ParamType::StringArray(12514849900987264429),
                    ParamType::StringArray(7017071859781709229),
                ],
                generics: vec![],
            }])
            .unwrap(),
            generics: vec![],
        }];
        let bytes = vec![];
        let a = ABIDecoder::default().decode_multiple(&param_types, &bytes);

at the decode_multiple step.
We should probably enforce some upper limit on the length of StringArray and Array.