scylla-2026.3.3-candidate-20261004023307: commitlog: Make replay large fragment cache per-(segment-)shard
Fixes: SCYLLADB-4945 Fragment ID for large commitlog entries are only unique per-shard. For a non-corrupt commitlog, this is not a problem, since we replay in descriptor order -> partitioned per shard. But if one or more segments are broken, we could end up with lingering data from one shard sharing id with a subsequent one from another shard. This can cause data corruption or data loss, depending…