[JIT-1412] Mempool example bugfixes

Notes:

Upgrade Solana version
Fixes broken mempool example in README
Perform pubkey verification at CLI startup

Fixes multiple pubkey issue:

➜  searcher-examples ✗ cargo run --bin jito-searcher-cli -- \
  --block-engine-url https://dallas.testnet.block-engine.jito.wtf \
  --keypair-path blockengine_testnet.json \
  mempool-accounts --accounts 7heQNXEtxSv3wV8sNbuQsDN5xNGbbpLvHGiyXuJxEf7n 96gYZGLnJYVFmbjzopPSU6QiEV5fGqZNyN9nmNhvrZU5
    Finished dev [unoptimized + debuginfo] target(s) in 0.15s
     Running `target/debug/jito-searcher-cli --block-engine-url 'https://dallas.testnet.block-engine.jito.wtf' --keypair-path /home/eric/dev/block-engine/blockengine_testnet.json mempool-accounts --accounts 7heQNXEtxSv3wV8sNbuQsDN5xNGbbpLvHGiyXuJxEf7n 96gYZGLnJYVFmbjzopPSU6QiEV5fGqZNyN9nmNhvrZU5`
error: unexpected argument '96gYZGLnJYVFmbjzopPSU6QiEV5fGqZNyN9nmNhvrZU5' found

For more information, try '--help'.

jito-labs / searcher-examples

[JIT-1412] Mempool example bugfixes #30