Add rewards_cli

[rickyrombo]

Manages the reward manager program's registered senders and lookup table

Usage:
  rewards_cli [command]

Available Commands:
  completion    Generate the autocompletion script for the specified shell
  help          Help about any command
  register      Register a single Ethereum address as a sender in the rewards program
  sync          Register all senders for validators
  update-lookup Update the address lookup table with new sender accounts

Flags:
      --dry-run               Dry run mode - check accounts without registering
  -h, --help                  help for reward_manager_senders
  -k, --keypair string        Fee payer keypair file (overrides env default)
  -o, --openAudioURL string   OpenAudio SDK URL (overrides env default)
  -r, --rpc string            Solana RPC endpoint (overrides env default)

Use "reward_manager_senders [command] --help" for more information about a command.

Tested by running against prod - updated the lookup table and the registered senders (did not deregister - those attestations are not live on OpenAudio)