[Bug] Unbounded deserialization of Proof `batch_sizes`

[vicsn]

🐛 Bug Report

CanonicalDeserialize for Vec<T> used by the following line is not bounded:

let batch_sizes: Vec<u64> = CanonicalDeserialize::deserialize_with_mode(&mut reader, compress, validate)?;

This is not a critical issue because our Message deserialization is capped at 128 MiB anyhow, which we're in the process of reducing: ProvableHQ/snarkOS#4055

But it would be nice to clean up at some point.