xtask: wait for sovereign rollup

[gabriele-0201]

In xtask/src/main.rs, instead of waiting for a specific amount of time, a method that mimics the behavior of the shim could be implemented. This way, we can avoid waiting for an arbitrary amount of time.

Similarly, in xtask/src/sovereing.rs, in the test_sovereign_rollup function, after submitting the batch, we wait for another arbitrary amount of time for the rollup to retrieve the transaction from the DA and begin processing them. Then, we can verify if the correct amount of tokens has been minted. As previously mentioned, having a more deterministic approach would be good