Compaction tasks executors serve two different purposes - as compaction
manager related entity they execute compaction operation and as task
manager related entity they track compaction status.
When one role depends on the other, as it currently is for
compaction_task_impl::done() and compaction_task_executor::compaction_done(),
requirements of both roles need to be satisfied at the same time in each
corner case. Such complexity leads to bugs.
To prevent it, compaction_task_impl::done() of executors no longer depends
on compaction_task_executor::compaction_done().
Fixes: #14912.
Closesscylladb/scylladb#15140
* github.com:scylladb/scylladb:
compaction: warn about compaction_done()
compaction: do not run stopped compaction
compaction: modify lowest compaction tasks' run method
compaction: pass do_throw_if_stopping to compaction_task_executor
45dfce6632