Currently it grabs one from database, but it's not nice to use database
as config/sched-groups provider.
This PR passes the scheduling group to use for sending hints via manager
which, in turn, gets one from proxy via its config (proxy config already
carries configuration for hints manager). The group is initialized in
main.cc code and is set to the maintenance one (nowadays it's the same
as streaming group).
This will help splitting the streaming scheduling group into more
elaborated groups under the maintenance supergroup: SCYLLADB-351
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
Closesscylladb/scylladb#28358
c61d855250