Add snapshot subcommand that creates a ledger snapshot from an archive

[leighmcculloch]

What

Add snapshot subcommand that creates a ledger snapshot from an archive.

Why

To make it possible to easily test against mainnet state.

Try it out

Install stellar-cli:

cargo install \
  --locked \
  --git https://github.com/stellar/stellar-cli \
  --branch snap \
  stellar-cli

Snapshot ledger:

stellar snapshot \
  --output json
  --address CCW67TSZV3SSS2HXMBQ5JFGCKJNXKZM7UQUWUZPUTHXSTZLEO7SJMI75 \
  --out snapshot.json

Write a test importing it:

#![cfg(test)]
use soroban_sdk::{token::TokenClient, Address, Env, String};

#[test]
fn test() {
    let e = Env::from_ledger_snapshot_file("snapshot.json");
    let contract = TokenClient::new(
        &e,
        &Address::from_string(&String::from_str(
            &e,
            "CCW67TSZV3SSS2HXMBQ5JFGCKJNXKZM7UQUWUZPUTHXSTZLEO7SJMI75",
        )),
    );
    let wallet = Address::from_string(&String::from_str(
        &e,
        "CAZ6W4WHVGQBGURYTUOLCUOOHW6VQGAAPSPCD72VEDZMBBPY7H43AYEC",
    ));
    assert_eq!(contract.balance(&wallet), 553804322934);
}

Close #383

[leighmcculloch]

Todo:

• automatically pickup trust lines and accounts that hold the asset of a stellar asset contract
• fix bug where a wasm could be inserted twice into the resulting snapshot
• make resulting snapshot reproducible and stable independent of input order whether inputs were derived or explicit