Coroutinization will help improve readability and allow easier changes planned for this code.
This work was separated from https://github.com/scylladb/scylladb/pull/17910 to make it smoother to review and merge.
Closesscylladb/scylladb#18788
* github.com:scylladb/scylladb:
cql3: coroutinize create/alter/drop service levels
auth: coroutinize alter_role and drop_role
auth: coroutinize grant_permissions and revoke_permissions
auth: coroutinize create_role
cql3: statements: co-routinize auth related statements
cql3: statements: release unused guard explicitly in auth related statements