The next index to be assigned to an incoming signed submission.
Every accepted submission is assigned a unique index; that index is bound to that particular
submission for the duration of the election. On election finalization, the next index is
reset to 0.
We can't just use SignedSubmissionIndices.len(), because that's a bounded set; past its
capacity, it will simply saturate. We can't just iterate over SignedSubmissionsMap,
because iteration is slow. Instead, we store the value here.
The next index to be assigned to an incoming signed submission.
Every accepted submission is assigned a unique index; that index is bound to that particular submission for the duration of the election. On election finalization, the next index is reset to 0.
We can't just use
SignedSubmissionIndices.len(), because that's a bounded set; past its capacity, it will simply saturate. We can't just iterate overSignedSubmissionsMap, because iteration is slow. Instead, we store the value here.