This change reorganizes the way standard_role_manager startup is handled: role_manager::ensure_superuser_is_created() is added, which returns a future that resolves once the superuser is available. We wait for this future before starting the CQL server.
There is a change in behavior auth::do_after_system_ready is potentially an infinite loop, and we await its result.
Fixes#10481
Reason for no backports: it's not a regresson and it's an issue that may only affect a tiny time window during the cluster startup.
Closesscylladb/scylladb#20137
* github.com:scylladb/scylladb:
test: test_restart_cluster: create the test
auth: standard_role_manager allows awaiting superuser creation
auth: coroutinize the standard_role_manager start() function
auth: don't start server until the superuser is created
63725b10a8