Reduce overhead of large numbers of snapshots in a single repository #66042
Description
We currently recommend SLM limit the number of snapshots to < 200 in a single repository, however, with searchable snapshots we are likely to exceed this number quickly. Thankfully searchable snapshot snapshots are of a single index and therefore less overhead in the repository.
Regardless, we should attempt to switch our overhead from something like:
O(snapshots * average_number_indices_per_snapshots)
to
O(indices_count)
As this would allow us to better support clusters with 10,000+ searchable snapshot backed indices.