This is a follow-up for #15279 and it fixes two problems.
First, we restore flushes on writes for the tables that were switched to the schema commitlog if `SCHEMA_COMMITLOG` feature is not yet enabled. Otherwise durability is not guaranteed.
Second, we address the problem with truncation records, which could refer to the old commitlog if any of the switched tables were truncated in the past. If the node crashes later, and we replay schema commitlog, we may skip some mutations since their `replay_position`s will be smaller than the `replay_position`s stored for the old commitlog in the `truncated` table.
It turned out that this problem exists even if we don't switch commitlogs for tables. If the node was rebooted the segment ids will start from some small number - they use `steady_clock` which is usually bound to boot time. This means that if the node crashed we may skip the mutations because their RPs will be smaller than the last truncation record RP.
To address this problem we delete truncation records as soon as commitlog is replayed. We also include a test which demonstrates the problem.
Fixes#15354Closesscylladb/scylladb#15532
* github.com:scylladb/scylladb:
add test_commitlog
system.truncated: Remove replay_position data from truncated on start
main.cc: flush only local memtables when replaying schema commitlog
main.cc: drop redundant supervisor::notify
system_keyspace: flush if schema commitlog is not available
c1486fee40