Fix potential returning account state twice: first from block, then from blockchain states

[dmugtasimov]

    def yield_account_states(self, from_block_number: Optional[int] = None):
        # TODO(dmu) HIGH: Reuse this method where possible
        block_number = self.get_last_block_number() if from_block_number is None else from_block_number
        if block_number == -1:
            yield from self.get_first_blockchain_state().yield_account_states()
            return

        blockchain_state = self.get_blockchain_state_by_block_number(block_number, inclusive=True)
        for block in self.yield_blocks_slice_reversed(block_number, blockchain_state.last_block_number):
            yield from block.yield_account_states()

        yield from blockchain_state.yield_account_states()