Add a method to SentTx to await for RPC server accounts to be fully synched

[spalladino]

Currently user needs to send it, await it separately, check it’s been mined, and sometimes await for the rpc server to sync to avoid race conditions.

We recently introduced the wait() method that handles the awaiting and check that it’s mined, but we’re still missing the check for account synchronised.

We should add another method (or a flag to wait) to make it explicit that we want to wait until all accounts on the RPC server have been synchronised up to the block in which the tx was mined, in other words, its side effects are visible when querying the RPC server.

Note that waiting only on the accounts that were involved in the tx should be enough (ie accounts that sent or received notes), but doing this filtering is not easy since we lose that information when we get to a SentTx, so it's easier to just wait on all accounts to be synched.