Ethan Reesor authored May 06, 2022 and Dennis B committed May 06, 2022

Closes AC-924. Implements sequence numbers for synthetic transactions. Every subnet tracks the number of synthetic transactions it has sent to and received from each other subnet.

The next step is to detect when a synthetic transaction is received out of sequence and leave it on the pending list until the missing synthetic transactions are received.

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Related to AC-924