The Shard::runAggregation function has been changed to have a "onRetry" callback that allows to write retryable aggregations. During the execution of the SPM-4003 project, we preferred using RetryPolicy::kStrictlyNotIdempotent to make backport easier and safer.

However, there's nothing preventing read only aggregation from being retried anymore and we should consider using RetryPolicy::kIdempotent in read only aggregations.