Syncing is slow when using deployed fullnode

[willemolding]

When syncing zingo-cli wallet using the lightwalletd server https://cartezcash-fullnode.fly.dev:443 the sync time is very slow. The main reason for the latency appears to be the round-trip time to retrieve blocks for processing.

Some thoughts on how to improve this

• Currently zingo is requesting each block individually and not using the batch functionality of lightwalletd. This is intentional for the moment as it locks up when making batch requests but this may help significantly.
• Scale up the fly.io deployment. It is currently running on a single low-tier machine
• Currently there is a bunch of other stuff happening in the block lookup loop https://github.com/willemolding/CarteZcash/blob/406f58b727331eef6e86a0880a33e87bdbfbd9ab/cartezcash-lightwalletd/src/service_impl.rs#L165. We can likely streamline this a lot