Sidecar: check user balance and nonce before sending commitments

[thedevbirb]

In the context of the recent proposal of account abstraction it may be possible that a transaction changes the balance of an EOA without increasing its nonce, since it can be originated by another entity.
As such, in the sidecar we should:

• wait for the right slot before sending the commitments and
• check both balance and nonce according to the current state

[mempirate]

@namn-grg another thing to research in the AA report is which incompatiblities there are with Bolt as of now

[thedevbirb]

Actually some balances checks are already implemented, see unstable branch as of now:

bolt/bolt-sidecar/src/builder/template.rs

Lines 86 to 116 in 025d296

	pub fn retain(&mut self, address: Address, mut state: AccountState) {
	let mut indexes = Vec::new();
	for (index, tx) in self.transactions.iter().enumerate() {
	let max_cost = max_transaction_cost(tx);
	if tx.recover_signer().expect("passed validation") == address
	&& (state.balance < max_cost || state.transaction_count > tx.nonce())
	{
	tracing::trace!(
	%address,
	"Removing transaction at index {} due to conflict with account state",
	index
	);
	indexes.push(index);
	// Continue to the next iteration, not updating the state
	continue;
	}
	// Update intermediary state for next transaction (if the tx was not removed)
	state.balance -= max_cost;
	state.transaction_count += 1;
	}
	// Remove transactions that conflict with the account state. We start in reverse
	// order to avoid invalidating the indexes.
	for index in indexes.into_iter().rev() {
	self.remove_transaction_at_index(index);
	}
	}
	}

Moreover, such logic has been a bit refactored by #117 as well.