[TASK] Batch Deposit Relaying for tx + reward trees: Event Listener

[akileshtangella]

• Event listener for the batched deposit queue.
  • Create autogen code in Rust for proxy contract in webb-rs repo. Add code to build.rs.
  • Create an event listener for MASP proxy. Leverage code from other event listeners.
  • Create an event handler that on a newly queued deposit, check if number of queued deposits is larger than batch size
  • Create an event handler that on a newly queued reward unspent/spent tree commitment, check if number of queued reward unspent tree commitment is larger than batch size
  • If it is, create a batch update proof and submit it back to proxy.