Rerequest foreign proposals after timeout

[sdbondi]

Problem

Currently if a foreign proposal is not received by any shard group (SG) member, the transaction will indefinitely remain unfinalized.

Proposal 1

After a certain time (could be block height or time-based) a validator should request the foreign proposal. The request would be "by transaction" as there is no way to know the foreign block ID.

Considerations:

• If the foreign proposal for a transaction does not exist on the remote end. After a timeout we should ABORT the transaction.
• The foreign node should be aware of the transaction because if they truly involve the transaction, the remote SGs should have sent their foreign proposal which would have lead to the foreign nodes sequencing it if it was not previously sequenced.