E2E test runs multi-column CAS workload (LOCAL_QUORUM/LOCAL_SERIAL) while
tablets are repeatedly migrated between nodes. Uncertainty timeouts are
resolved via LOCAL_SERIAL reads; guards use max(row, lower_bound). Final
assertion: s{i} per (pk,i) equals the count of confirmed CAS by worker i
(no lost/phantom updates) despite tablet moves.
Closes scylladb/scylladb#25402