This series adds an async guard to system_keyspace operations
and adds a deferred action to stop the system_keyspace in main() before destroying the service.
This helps to make sure that sys_ks is unplugged from its users and that all async operations using it are drained once it's stopped.
* Enhancement, no backport needed
Closesscylladb/scylladb#23113
* github.com:scylladb/scylladb:
main: stop system keyspace
system_keyspace: call shutdown from stop
system_keyspace: shutdown: allow calling more than once
database, compaction_manager, large_data_handler: use pluggable<system_keysapce>
utils: add class pluggable
2bb455ec75