Function is_decomposed_amount 

pub fn is_decomposed_amount(amount: &u64) -> bool

Checks that an output amount is decomposed.

This is also used during miner tx verification.

ref: https://monero-book.cuprate.org/consensus_rules/transactions/ring_signatures.html#output-amount ref: https://monero-book.cuprate.org/consensus_rules/blocks/miner_tx.html#output-amounts