Update encoding/decoding according to new specs

[nedsalk]

As of the time of writing, the transaction specs are outdated, but internal discussions led to the conclusion that all of the fields listed below should be updated from u16 to u32 in our encoding/decoding logic:

• InputMessage.predicateLength (InputCoin.predicateLength was updated in feat: increase supported predicate length in transactions #1033),
• InputMessage.predicateDataLength, (InputCoin.predicateDataLength was updated in feat: increase supported predicate length in transactions #1033),
• InputMessage.dataLength,
• TransactionScript.scriptLength,
• TransactionScript.scriptDataLength,
• TransactionCreate.bytecodeLength,
• Witness.dataLength