## Description 

This PR adds the support for user to pass in `--latest` while
downloading snapshots. This is going to be super useful for first time
users trying to run a testnet or mainnet sui fullnode locally (where
they don't want to fist find out the latest epoch somehow first) and
make running a fullnode for the first time a more convenient process
## Test Plan 

```
(base) sadhansood@Sadhans-Laptop sui % cargo run -p sui-tool download-db-snapshot --genesis ~/Downloads/genesis.blob --formal --network mainnet  --path /opt/sui/db/authorities_db --num-parallel-downloads 50 --no-sign-request --snapshot-bucket-type=s3 --verbose --latest
    Finished dev [unoptimized + debuginfo] target(s) in 0.81s
     Running `target/debug/sui-tool download-db-snapshot --genesis /Users/sadhansood/Downloads/genesis.blob --formal --network mainnet --path /opt/sui/db/authorities_db --num-parallel-downloads 50 --no-sign-request --snapshot-bucket-type=s3 --verbose --latest`
Warning: download-db-snapshot --formal is deprecated. Please use download-formal-snapshot.
Beginning formal snapshot restore to end of epoch 279, network: Mainnet
2024-01-17T23:50:31.015392Z  INFO sui_tool: Starting summary sync
```