Sylvain R. authored Mar 23, 2022 and Marge Bot committed Apr 04, 2022

Before this patch, withdrawing an asset from a transaction rollup
worked as follows.

  1. A `Withdraw' operation in the layer-2 has to be batched and
     submitted to the layer-1
  2. A commitment for this batch has to be posted to the layer-1
  3. Once this commitment is finalized, a `Tx_rollup_withdraw'
     operation can be submitted

This logic does not play well with commitment merklisation, because it
implies providing the same proof several time (the proof about the
message_result_hash being part of the commitment).

As a consequence, we refine this logic by adding a new operation,
`Tx_rollup_dispatch_tickets', which is used to handle all the
withdrawals of a given batch at once. Then, we introduce
`Transfer_tickets', which allows implicit accounts to give tickets
back to smart contracts.

Co-authored-by: Thomas Letan <lthms@nomadic-labs.com>