* Use efficient comm for balances
At the moment we're using merkle trees even though we don't need
inclusion proofs, which means we're calculating more hashes than
necessary and limiting the account set size to 256.
This change is a temporary solution that chooses a more efficient
way to calculate a commitment to the account balances, while we
wait for something more scalable like a Verkle Tree.
* remove leftover constants
* aat: integrate withdraw with CL
* aat: withdrawal passes!
* aat: cleanup withdrawals a bit
* aat: move Ptx{Input|Output|Private to cl::partial_tx
* aat: zone_state zone transition validation coded w.r.t. metadata
* aat: rename meta to in_meta in zone transition validation
